I sense that fighting on the ground would be near impossible upside down.. but theres not reason why to let all the work that went into this mode go to waste. try setting:
engage distance -80
engage hight 1000
with a dojo and stuff like that. if you want the fight to continue on the ground, set high DM and low Grav. if you want it to be an air fight, set low DM and high grav.
with the negative engage distance, the firs thing people do is grab their apponents and then swing them around.
its interesting to see which one gets the upper hand. landing head down defintly in not hte way to go.
I ve tried this out right side up in multiplayer, and Ive concluded it would be interesting to see what would happen if the players were upside down. try it.