On Wednesday, November 18, 2020 at 11:29:38 AM UTC-8, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
Basically what I was thinking of doing. Take a blank 57mm hole cover plate and drill a 57mm (2-1/4") hole in the middle of it. I would add rivnuts as I find myself flinging swear words at instruments that use loose nuts and bolts. Then drill and countersink the 4 rectangular spaced holes into the hole cover to attach the control head. Boom.
John,

I think I have two sets of the adapters, I'll look and send you a PM.

Mike B.