Matt, I have made some progress and am pretty close to finishing the mount. It is not nearly as neat and refined as yours, but it is after all my first attempt. Since I am at a lack for tooling to cut and tap the maple blocks accurately, I decided to simply use the blind nuts as you did in your first unit in the thread.

I found an inner tube that fits as you described earlier in the thread - snug but not tight.

My only remaining questions are 1) do you give the mount some overall coating of epoxy or something for fuel proofing a bit and 2) what is the "rubber bumper stock" that you mentioned above (just a donut from the inner tube??) and is it glued in at all, or glued in on one side of the inner faces of the donut spacer?

Thanks much! The finish line is in sight!