diff --git a/libraries/AP_HAL_ChibiOS/Scheduler.h b/libraries/AP_HAL_ChibiOS/Scheduler.h
index eea99da8da..fa9c6cb817 100644
--- a/libraries/AP_HAL_ChibiOS/Scheduler.h
+++ b/libraries/AP_HAL_ChibiOS/Scheduler.h
@@ -60,7 +60,7 @@
 #endif
 
 #ifndef RCOUT_THD_WA_SIZE
-#define RCOUT_THD_WA_SIZE    1024
+#define RCOUT_THD_WA_SIZE    512
 #endif
 
 #ifndef RCIN_THD_WA_SIZE
@@ -72,11 +72,11 @@
 #endif
 
 #ifndef STORAGE_THD_WA_SIZE
-#define STORAGE_THD_WA_SIZE 1536
+#define STORAGE_THD_WA_SIZE 1024
 #endif
 
 #ifndef MONITOR_THD_WA_SIZE
-#define MONITOR_THD_WA_SIZE 768
+#define MONITOR_THD_WA_SIZE 512
 #endif
 
 /* Scheduler implementation: */
diff --git a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
index 529bbf4373..ad6490d1ed 100644
--- a/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
+++ b/libraries/AP_HAL_ChibiOS/UARTDriver.cpp
@@ -79,7 +79,7 @@ static const eventmask_t EVT_TRANSMIT_UNBUFFERED = EVENT_MASK(3);
 #endif
 
 #ifndef HAL_UART_RX_STACK_SIZE
-#define HAL_UART_RX_STACK_SIZE 1024
+#define HAL_UART_RX_STACK_SIZE 768
 #endif
 
 UARTDriver::UARTDriver(uint8_t _serial_num) :