In case anyone is interested, I have made this speed measurement on flat concrete.

My rustler is totally stock except the FLM extended chassis.

It was powered by two 3S1P A123 packs in parallel.

Result was : 48mph (77km/h), using a bushnell radar gun.
Measurements were very consistent run after run!

I have not made any measurement with a single A123 3S1P pack, but I suspect it can go a little faster (more lightweight) maybe 50mph