Losi plastic and screws really suck, I'm having to replace almost every screw in my Muggy because I'm shearing and bending pretty much everything. Stock control arms are garbage, IDK if the RPM arms with the LST2/Muggy adapters will fit the XXL but they are MUCH tougher.
I don't know of any better bumper for it, but I haven't had any issues with mine. The braces are about to crack in half but I may just have to replace them with more stock pieces.
That Neu is way too high of a KV, it'll pull some serious amps and everything will run hot. I'd look into a 1Y (around 1,700 KV I think) on 5s. Satttheman has a video of his Muggy with a 1521/1Y on 6s and it's insanely powerful.
http://www.rc-monster.com/forum/show...6&postcount=41
I still haven't figured out a good wheelie bar, I just have to avoid jabbing at the throttle until the CD unloads enough power

I have sheared heads off of several screws (got pics of the screws on my phone for proof

) because of using the wing as a wheelie bar. Right now it looks like throttle control is the best and the wing can help but don't rely on it.