[rotorwrench]

It seems like a lot of frames are crusty in that area depending on time and the elements. That can have an effect. If the rubber is too thick, it may extrude more around the sides when tightening the bolt to bushing fit. If the bushings are too long, that could be a problem. At least one of the pads should protrude into the frame holes to get a good bearing surface for the bushing fit or it could slip off center. A lot of rubber cushion designs will wear through that rubber till they are metal to metal depending on the design of the cushion. The whole pad cushion surface should have some preload.

I just wonder if some are thicker to compensate for frame surface condition. It's kind of risky to assume such things but now days, quality control can be non existent too.