My APM2 is hidden inside my quad, and I would like to expose the "armed" LED by running a lead from one of the open connectors to an external LED.

I've got the code ready, but I'm not sure what port to use.  What's the open port range?  Any port to avoid, perhaps because it's commonly used for another user-level extension?

#if CONFIG_APM_HARDWARE == APM_HARDWARE_APM1
# define A_LED_PIN 37
#define A_LED_PIN_MIRROR    (what value for APM1?)

#elif CONFIG_APM_HARDWARE == APM_HARDWARE_APM2
# define A_LED_PIN 27
#define A_LED_PIN_MIRROR (what value for APM2?)

If there's interest I'll submit the change to the dev group.