Yes, I have seen the results of using rubber blocks. They usually fail. The rubber will compress and extrude under the constant pressure, causing body alignment problems and loose body bolts. (The thin pads do extrude a little, but not enough to matter).
One could use an aluminum block, or fabricate a steel spacer but these do not have the vibration deadening that wood does.
A fiber filled non extruding plastic could work, but the cost and effort would be way more than the wood blocks.