diff --git a/apps/px4io/controls.c b/apps/px4io/controls.c
index 37872d3569..21b4edcc37 100644
--- a/apps/px4io/controls.c
+++ b/apps/px4io/controls.c
@@ -167,7 +167,7 @@ controls_tick() {
 
 				int16_t scaled = raw;
 
-				/* adjust to zero-relative around center */
+				/* adjust to zero-relative around center (nominal -500..500) */
 				scaled -= conf[PX4IO_P_RC_CONFIG_CENTER];
 
 				/* scale to fixed-point representation (-10000..10000) */
diff --git a/nuttx/configs/px4io/io/defconfig b/nuttx/configs/px4io/io/defconfig
index 1145fb349f..bb937cf4ee 100755
--- a/nuttx/configs/px4io/io/defconfig
+++ b/nuttx/configs/px4io/io/defconfig
@@ -541,7 +541,7 @@ CONFIG_BOOT_COPYTORAM=n
 CONFIG_CUSTOM_STACK=n
 CONFIG_STACK_POINTER=
 CONFIG_IDLETHREAD_STACKSIZE=1024
-CONFIG_USERMAIN_STACKSIZE=800
+CONFIG_USERMAIN_STACKSIZE=1200
 CONFIG_PTHREAD_STACK_MIN=512
 CONFIG_PTHREAD_STACK_DEFAULT=1024
 CONFIG_HEAP_BASE=