you can always add the chassis plate later if you find you need it. Dafni lost a diff pinion because of the chassis flex at the RCM bash, and designed that plate with mike - which fixed his chassis flex problem. i think it had more to do with the jumps on that particular track though. but you can try the truck stock and if it flexes too much - add the plate later.
BUT - the front knuckles are indeed plastic. Xray makes aluminum knuckles and rear hub carriers as options, but i just wanted to let you know in case that's a deal-breaker (which it shouldn't be). they also make aluminum front and rear braces, if your heart is set on that too.
