No I don't use the bushings. The thick 4130 plate doesn't bend, and I tighten the bolts evenly so the clamping force is uniform. I would wager I would do
airframe damage before I would shear the bolts in a bad landing.

Have had it this way for a long time now, and no problems, and better yet
no worries .... AN-3's make no sense back there.

I look at a lot of REALLY nicely engineered solutions to the problem, and
I have to admit they look really good. BUT I don't think they provide any
better solution, than simply using AN-4's and a thicker plate ...

Jeff