I would just add that the composite front arm inserts give a little in the event of a hard crash when compared to the aluminum ones. The nice thing about that is it saves the lower carbon fiber arms from shattering. I have only broken one lower arm in 2 seasons and that was this past weekend at SeaTac when I got punted into the concrete drivers stand during a practice run. I personally would save the $40 and stick with the stock part as they really arent sloppy at all.
The only hop ups I run are the carbon fiber chassis and rear pod and different side and front springs. The rest of my 12r6 is box stock.