[Mart]

I'm a little out of my depth here, but this is an interesting subject. The thing that occurs to me though, is that it is an offset of the cam lobe to the lifter centre that promotes a rotation in the lifter. The radius may be a red herring as far as rotation is concerned. If the cam lobe wiped directly across the centre of the lifter it would not want to rotate. Offset that wipe area and the lifter will receive a little rotational push every time.

Mart.