I like zero rebound at our club track, my truggy is planted and eats up the rough like no other. I would add rebound if I was having a hard time clearing any of our jumps. You do what suits your driving style the most.
All you have to do at the track to tune in your rebound is back the cap off a couple of turns, put the shock shaft where you want it, and tighten the cap back up..after that, you drive through that section a few times and see what you think.