
I have the left image situation, but a little lower, as the washer is under the top plate. I mounted a small ball on it (30mm) and it plays perfect for the classics.
Oh, I didn't even think to try a smaller ball top, and I have one for a JLW that I'm going to make a Stargate-style controller panel out of!
I tried it and I think I like it better! Thanks!
The mounting kit from Ultimarc has the wood inserts to avoid having screws on the top of the panel when bottom mounting. They are 1/2" thick, so I may go ahead and route 1/4" in the bottom (did 1/2" last time like the picture) so that the ball is 1/4" closer to the surface than it is now and so that I can use the inserts. I think that'll solve two problems for me.

I'll be ordering more small balltops from lizardlick as well! Thanks for reminding me about that!