but the polyurethane bushings tend to squeeze out the sides of the arm holes. If they protrude past the center sleeve, they will bind horribly. Then, it will feel like you have no springs in the rear. I just finished trimming most of my poly bushings and ride quality is plush but controlled!
Polyurethane bushings also need to be lubricated about once per year. I would drill and tap a hole in each bushing for a zerk fitting.
The warning on CZP is a load of bs-- if you properly trim and lubricate your poly bushings. ;)