I like the original secondary mount on my Fullerscope- it cleverly separates the tilt from the rotate of the mirror but it’s a bit crude and too big for my new mirror. The new design is meant to be kinematic and I think it is It tilts the mirror on a ball joint and axial rotation is locked by a sliding key way on one of the adjuster screws. There are 2 adjuster screws opposed by strong springs and the second screw and the springs bear down on a nylon swash plate to make the action smooth. The nice thing about the ball joint is it puts the point of rotation just behind the centre of the mirror so lateral motion should be reduced. The mirror will be supported around its edge in a brass thin wall tube like the AstroSystems holders.
Here’s the new mirror- a quartz one from Protostar, and the design of the mount.