The .5 is a sweet car and has an incredibly tough drivetrain. It handles fantastically and should be up to anything you want to do with it.
My lastest and favorite setup is a medusa 2200 50mm motor on
4S 25C 2100 Zippy lipos, controlled by a sidewinder. The 35mm wide lipos fit nicely on the Ofna chassis and the higher voltage allows the use of the cheaper controller and also lower temps. The controller is easier to program too as the usb port on the MM is never in the right place.
I also use a Neu 30C 2500 pack, but the Zips are hard to beat for the price and put out just as much power. I even put on Masher2000s on Jato rims for off roading and good clearance. 1/10 buggy or truck tires for the track.
Mike's chassis is also very nice, and the longer wheelbase would help. The .5 is small enough its a lot less forgiving in the air vs the fullscale 1/8th trugs, so it makes you drive better. It is incredibly light and nimble.