I had a RC8Te paired with the RX8/2000 combo on 5s lipo, and it ran very well. Battery is only 4200 mah. but with mixed driving it gave me more or less 20 min.
For maximize runtimes, you have to use small gearing and efficient motor.
That's mean low kV and High voltage. Tekin truggy motor 1300kV on 6s would be perfect. I say tekin truggy version because buggy version aren't very powerfull and heat a little in buggy, and its drop the efficiency of the motor...