( I think ) Anyone with any common sense will be able to realise whats a realistic and whats an unrealistic setup given their setup- larger, heavier vehicles will require heavier duty lipos and limit/ reduce their gearing as required. As it is, using a calculator (like BrianG's, though there are others out there) will tell you the required ratio to hit any given speed, and gearing for a certain speed is the key thing- manufacturers can provide info on the tranny & diff ratios and tire diameter etc, then you just factor that in with the rpms (kv x volts) to get the required gearing for any given
realistic speed.
Like I said, common sense + gearing calculator = success.
