[craig]

In theory, the amount of anti-squat is solely from the angle of the upper and lower arms which dictates your Instant Center location and Side View Swing Arm Length. The bushing pictured will need to flex, so it either has to be rubber or, better yet, a spherical bearing.

It looks like you could stiffen that bushing by increasing the tension with those nuts, but that would have no affect on the geometrical anti-squat. But maybe creating a physical bind in the suspension to limit squat is an acceptable practice? Most likely not.

Craig