I tested the autopilot, with compass only, no wind input, on my Weta last summer and it worked!! :o
Added knobs for P I D setting so I could tune them in real-time. Added a OpenLOG to log everything. Locked on course, it steered the boat impressively well. Next step is to add the actual wind input and make it steer to a wind angle. This is probably going to be tested on a much bigger boat, like a Maxi Fenix.