C4.2 body won't work. At least it didn't seem like it would when I set it over the chassis.
I removed the rib behind the servo just to free up a few extra mm of space for electronics.
I mounted my transponder in the front of servo. I choose to go with the short servo due to weight, it saved me 21 grams over the full size one.
Car weighed 1520g last night with short pack and servo. Only other changes was a few Ti and aluminum screws but everything on bottom of car was still steel.