I've been running a second hand X6² for a few weeks, I decided to saddle-pack the chassis - after having removed the necessary material, I became a little concerned about chassis strength.
So I made some 6mm aluminium chassis braces; The third screw in the middle of the brace can be added or left out so as to be able to tweak flex.
Hope you like it
Btw: the car handles like a dream on astro

However, all tips are welcome to get it to handle on dusty, hard-packed clay