I reworked the HPI Flux motor mount that serves as a rear motor support on my XXL. I made it thinner and lighter and did some sanding to make it look purdier. I also installed one of my 8th scale CDs in the tranny. It has something like 250k in it so it is stiff but still unloads a bit. Wheelies are still there but are more controllable.
Last I stripped a wheel with the Losi 17 mm hexes I installed. I measured the size of the Losi hexes compared to Traxxas hexes I had and wasn't using.
Losi: 16.87 mm
Traxxas: 16.97 mm
The bigger size of the Traxxas hexes should result in a snugger fit in the wheels with less chance of stripping them so I modified them to fit.