Nerfing the flippers is super easy. It will be in Hazards.py under class HellRaiser like apanx said. You want to edit this line:
self.hinge.SetPowerSettings(80,1500)
This will affect any other arena that uses class HellRaiser too, so make a copy like apanx said if you don't want nerfed flippers in every arena. (I don't think there are any others in stock but some custom arenas use class HellRaiser.)
Another good way to do it would be to edit the angle limits of the hinge in the gmf, to make it have a smaller travel arc. Instead of turning bots over completely, it could just pop them up a bit without flipping them (usually), kinda like the Battlebots Hellraisers.
Editing the stock arena gmfs is kind of a pain though. Dummy's compiler doesn't like node parents, and Serge's doesn't like lights. I think it's possible though.