I actually mounted the auto pilot servos twice. I did it once, waited a few weeks and decided I didn't like it, and then reconfigured everything and did it again.
To make the mounting plate I first used a piece of lexan to develop the shape and locate where all holes for the mounting provisions needed to be. Then I used this as a pattern to cut the final mounting plate out of 1/8" aluminum.
I made the mounts out of 1/16" aluminum. I created the mounts in my CAD system, printed out full size copies which were contact cemented to the aluminum for cutting and bending.
I am happy with the final outcome. Very compact, but easy to access under the passenger seat.
