diff --git a/g2core/canonical_machine.cpp b/g2core/canonical_machine.cpp
index 6c12154a..2722158f 100644
--- a/g2core/canonical_machine.cpp
+++ b/g2core/canonical_machine.cpp
@@ -367,7 +367,7 @@ void cm_set_tool_number(GCodeState_t *gcode_state, const uint8_t tool)
 void cm_set_absolute_override(GCodeState_t *gcode_state, const uint8_t absolute_override)
 {
     gcode_state->absolute_override = (cmAbsoluteOverride)absolute_override;
-    cm_set_work_offsets(MODEL);         // must reset offsets if you change absolute override
+//    cm_set_work_offsets(MODEL);         // must reset offsets if you change absolute override
 }
 
 void cm_set_model_linenum(const uint32_t linenum)
@@ -2082,7 +2082,7 @@ stat_t cm_set_tn(nvObj_t *nv) { return (set_float(nv, cm->a[_axis(nv)].travel_mi
 stat_t cm_get_tm(nvObj_t *nv) { return (get_float(nv, cm->a[_axis(nv)].travel_max)); }
 stat_t cm_set_tm(nvObj_t *nv) { return (set_float(nv, cm->a[_axis(nv)].travel_max)); }
 stat_t cm_get_ra(nvObj_t *nv) { return (get_float(nv, cm->a[_axis(nv)].radius)); }
-stat_t cm_set_ra(nvObj_t *nv) { return (get_float(nv, cm->a[_axis(nv)].radius)); }
+stat_t cm_set_ra(nvObj_t *nv) { return (set_float_range(nv, cm->a[_axis(nv)].radius, RADIUS_MIN, 1000000)); }
 
 /**** Axis Jerk Primitives
  * cm_get_axis_jerk() - returns jerk for an axis
diff --git a/g2core/canonical_machine.h b/g2core/canonical_machine.h
index 48d1fdb1..a204d9b6 100644
--- a/g2core/canonical_machine.h
+++ b/g2core/canonical_machine.h
@@ -47,8 +47,9 @@
 
 #define DISABLE_SOFT_LIMIT (999999)
 #define JERK_INPUT_MIN (0.01)               // minimum allowable jerk setting in millions mm/min^3
-#define JERK_INPUT_MAX (1000000)             // maximum allowable jerk setting in millions mm/min^3
+#define JERK_INPUT_MAX (1000000)            // maximum allowable jerk setting in millions mm/min^3
 #define PROBES_STORED 3                     // we store three probes for coordinate rotation computation
+#define RADIUS_MIN (0.0001)                 // minimum value for ABC radius settings
 
 /*****************************************************************************
  * MACHINE STATE MODEL
diff --git a/g2core/config_app.cpp b/g2core/config_app.cpp
index 00590e53..f55aa324 100644
--- a/g2core/config_app.cpp
+++ b/g2core/config_app.cpp
@@ -669,15 +669,15 @@ const cfgItem_t cfgArray[] = {
     { "", "er",  _f0, 0, tx_print_nul,  rpt_er,    set_nul,   (float *)&cs.null, 0 },   // get bogus exception report for testing
     { "", "qf",  _f0, 0, tx_print_nul,  get_nul,   cm_run_qf, (float *)&cs.null, 0 },   // SET to invoke queue flush
     { "", "rx",  _f0, 0, tx_print_int,  get_rx,    set_nul,   (float *)&cs.null, 0 },   // get RX buffer bytes or packets
-    { "", "dw",  _f0, 0, tx_print_int,  st_get_dw, set_nul,   (float *)&cs.null, 0 },   // get dwell time remaining
+    { "", "dw",  _f0, 0, tx_print_int,  st_get_dw, set_noop,  (float *)&cs.null, 0 },   // get dwell time remaining
     { "", "msg", _f0, 0, tx_print_str,  get_nul,   set_noop,  (float *)&cs.null, 0 },   // no operation on messages
     { "", "alarm",_f0,0, tx_print_nul,  cm_alrm,   cm_alrm,   (float *)&cs.null, 0 },   // trigger alarm
     { "", "panic",_f0,0, tx_print_nul,  cm_pnic,   cm_pnic,   (float *)&cs.null, 0 },   // trigger panic
     { "", "shutd",_f0,0, tx_print_nul,  cm_shutd,  cm_shutd,  (float *)&cs.null, 0 },   // trigger shutdown
     { "", "clear",_f0,0, tx_print_nul,  cm_clr,    cm_clr,    (float *)&cs.null, 0 },   // GET "clear" to clear alarm state
-    { "", "clr",  _f0,0, tx_print_nul,  cm_clr,    cm_clr,    (float *)&cs.null, 0 },   // synonym for "clear"
-    { "", "tick", _f0,0, tx_print_int,  get_tick,  set_nul,   (float *)&cs.null, 0 },   // get system time tic
-    { "", "tram", _f0,0, cm_print_tram,cm_get_tram,cm_set_tram,(float *)&cs.null, 0 },  // SET to attempt setting rotation matrix from probes
+    { "", "clr", _f0, 0, tx_print_nul,  cm_clr,    cm_clr,    (float *)&cs.null, 0 },   // synonym for "clear"
+    { "", "tick",_f0, 0, tx_print_int,  get_tick,  set_nul,   (float *)&cs.null, 0 },   // get system time tic
+    { "", "tram",_f0, 0, cm_print_tram,cm_get_tram,cm_set_tram,(float *)&cs.null, 0 },  // SET to attempt setting rotation matrix from probes
     { "", "defa",_f0, 0, tx_print_nul,  help_defa,set_defaults,(float *)&cs.null,0 },   // set/print defaults / help screen
     { "", "flash",_f0,0, tx_print_nul,  help_flash,hw_flash,  (float *)&cs.null,0 },
 
diff --git a/g2core/cycle_feedhold.cpp b/g2core/cycle_feedhold.cpp
index dba2d29c..e4c059d7 100644
--- a/g2core/cycle_feedhold.cpp
+++ b/g2core/cycle_feedhold.cpp
@@ -348,8 +348,8 @@ static void _sync_to_p1_hold_entry_actions_done(float* vect, bool* flag)
 static stat_t _run_p1_hold_exit_actions()     // LATER: if value == true return with offset corrections
 {
     // perform end-hold actions --- while still in secondary machine
-    spindle_control_sync(SPINDLE_RESUME);               // resume spindle if paused
     coolant_control_sync(COOLANT_RESUME, COOLANT_BOTH); // resume coolant if paused
+    spindle_control_sync(SPINDLE_RESUME);               // resume spindle if paused
     
     // do return move though an intermediate point; queue a wait
     cm2.return_flags[AXIS_Z] = false;
diff --git a/g2core/error.h b/g2core/error.h
index 4f4024c9..06884f5d 100644
--- a/g2core/error.h
+++ b/g2core/error.h
@@ -205,7 +205,6 @@ char *get_status_message(stat_t status);
 #define STAT_MAX_DEPTH_EXCEEDED 115             // JSON exceeded maximum nesting depth
 #define STAT_VALUE_TYPE_ERROR 116               // JSON value does not agree with variable type
 
-//#define STAT_ERROR_DEVICE_NOT_ACTIVE 117        // Device cannot receive commands at this time
 #define STAT_INPUT_FROM_MUTED_CHANNEL_ERROR 117 // input from a muted channel was ignored
 #define STAT_ERROR_118 118
 #define STAT_ERROR_119 119
diff --git a/g2core/planner.cpp b/g2core/planner.cpp
index a7a5877c..8224af74 100644
--- a/g2core/planner.cpp
+++ b/g2core/planner.cpp
@@ -200,9 +200,11 @@ void planner_init(mpPlanner_t *_mp, mpPlannerRuntime_t *_mr, mpBuf_t *queue, uin
     _mr->p = &_mr->bf[1];
 }
 
-void planner_reset(mpPlanner_t *_mp)
+void planner_reset(mpPlanner_t *_mp)    // reset planner queue, cease MR activity, but leave positions alone
 {
-    planner_init(_mp, _mp->mr, _mp->q.bf, _mp->q.queue_size);  // reset parent planner and linked Q and MR
+//    planner_init(_mp, _mp->mr, _mp->q.bf, _mp->q.queue_size);  // reset parent planner and linked Q and MR
+//    _mp->mr.block_state == BLOCK_INACTIVE;
+    _init_planner_queue(_mp, _mp->q.bf, _mp->q.queue_size);
 }
 
 stat_t planner_test_assertions(const mpPlanner_t *_mp)
diff --git a/g2core/settings.h b/g2core/settings.h
old mode 100755
new mode 100644
index eaa2fb7d..5fd3b12e
--- a/g2core/settings.h
+++ b/g2core/settings.h
@@ -2,7 +2,7 @@
  * settings.h - default runtime settings
  * This file is part of the g2core project
  *
- * Copyright (c) 2010 - 2016 Alden S. Hart Jr.
+ * Copyright (c) 2010 - 2017 Alden S. Hart Jr.
  *
  * This file ("the software") is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License, version 2 as published by the
@@ -35,6 +35,8 @@
 #ifndef SETTINGS_H_ONCE
 #define SETTINGS_H_ONCE
 
+#include "canonical_machine.h"
+
 /**** MACHINE PROFILES ******************************************************
  *
  * Provide an optional SETTINGS_FILE in the makefile or compiler command line:
@@ -54,4 +56,17 @@
 // The defaults below generally disable that function
 #include "settings/settings_default.h"
 
+// compile-time assertions - mostly checking the settings are not impossible
+
+#define stringify2(a) #a
+#define stringify(a) stringify2(a)
+
+//static_assert ( bool_constexpr , message ) // bool_constexpr must be true or assertion will fail
+static_assert ( (A_RADIUS > RADIUS_MIN), "A axis radius must be more than " stringify(RADIUS_MIN) ", but is " stringify(A_RADIUS) );
+static_assert ( (B_RADIUS > RADIUS_MIN), "B axis radius must be more than " stringify(RADIUS_MIN) ", but is " stringify(B_RADIUS) );
+static_assert ( (C_RADIUS > RADIUS_MIN), "C axis radius must be more than " stringify(RADIUS_MIN) ", but is " stringify(C_RADIUS) );
+
+#undef stringify 
+#undef stringify2
+
 #endif  // End of include guard: SETTINGS_H_ONCE
diff --git a/g2core/stepper.cpp b/g2core/stepper.cpp
index 0b7828af..9bf39acc 100644
--- a/g2core/stepper.cpp
+++ b/g2core/stepper.cpp
@@ -603,9 +603,7 @@ static void _load_move()
     // handle dwells and commands
     } else if (st_pre.block_type == BLOCK_TYPE_DWELL) {
         st_run.dwell_ticks_downcount = st_pre.dwell_ticks;
-
-        // We now use SysTick events to handle dwells
-        SysTickTimer.registerEvent(&dwell_systick_event);
+        SysTickTimer.registerEvent(&dwell_systick_event); // We now use SysTick events to handle dwells
 
     // handle synchronous commands
     } else if (st_pre.block_type == BLOCK_TYPE_COMMAND) {