What you really need is befriend a properly rated maintenance technician who is willing to act in a common sense manner...
I actually got the FAA Small Airplane directorate to sign off on connecting my handheld GPS
to a device that translated it's CDI outputs into course guidance
, and then connect that as a navigation input to my certified autopilot
. All it really took is finding the people in the FAA who operate in the "common sense zone"
and have a couple good hearted conversations...
A couple weeks later, presto! Done!
If you are near Sacramento, stop by Lincoln (KLHM) and talk to me... Or later this year I'll be based at KECP
Cheers!