The rear bumper looks like it's for the Evader DT, and mounts to the body I believe. Basically it's for appearance than functionality.
There should be a foam battery "spacer" in the rear of the tray...take it out for 7 cell use. I can't confirm this as I only ever ran 6 cell NiMh packs. Just check the measurements.
Performance? If just wanting more speed, I'd buy a lower turn brushed motor that you can replace the brushes on. Then this will mean a new ESC is needed as well since the Sprint is only rated for the lower end of the motor spectrum. The other option is to go with a "bottom of the barrel" 60A brushless motor/ESC combo that are found all over the www. I don't want to steer you in the wrong direction, or possibly get you into a product that has quality control issues. So, the safe generic answer from me will be to suggest a $70 HobbyWing EZRun 60A ESC/motor combo.
Last edited by RustyUs; 07-23-2016 at 03:02 AM.