RE: aluminum parts vs plastic parts
Plastic is what you want for bashing, and aluminum seems to me to be more for show. The plastic parts will flex and return to normal shape under stress, and if they stress too hard they will break. That's okay because plastic parts are really cheap to replace. When aluminum stresses, it's in general less likely to bend and break, but, if it bends, it won't return to its original shape. im no expert just my knowledge on the subject.
Check out [link=http://www.rcuniverse.com/forum/m_8970893/anchors_8970893/mpage_1/key_/anchor/tm.htm#8970893]THIS[/link] thead for a lot of discussion on the aluminum vs plastic battle.