The dash is not strong enough to mount a real oh-**** handle to IMO. I know you said you don't have any chance of a roll-over, so if that is the case you would prolly be alright.
Personnally I think the dash is too far away to reach if you are strapped into the seat right (think 4-5 pt harness). There is no excuse for a passenger to not be buckled in tight. As a driver I will ride w/ my top harness loose so I can look out the side to see were I am putting my tires. Whatever you do just make sure you don't put a grab bar were someones hand can get crushed in a roll. I made mine in the center of the rig as part of the cage. I stole the idea from Dan Dibble's buggy & Frankie's Offroad. specs are 1.25" DOM & It runs front to back the length of the cage. It is mounted to the tube that runs down the center of the cage.
Sorry for the big pics I didn't feel like re-sizing.