RE: aluminum parts vs plastic parts
IMO, if you can buy the part from RPM, then buy the RPM part. I've never seen an RPM piece break and the lifetime warranty is very comforting. I, for the most part, don't like using much aluminium. Hub carriers, a-arm mounts, and a few other random pieces are nice to have in aluminium for both rigidity, lack of wear, and durability. Aluminium shock towers, a-arms, bumpers, etc... aren't really necessary and will probably just end up getting bent eventually. Aluminium is also almost always going to be heavier than it's plastic or carbon counterparts.