Hard grab handles aren't worth the risk in my opinion...IF you "test" it for head clearance sitting in your seat I'd be willing to bet that in a nasty wreck your head will be several inches closer to that brain smashing bar than when you leaned forward testing it for clearance..
Not saying the belt is stretching, I'm saying you are under tremendous G forces and every bit of slack in that belt is taken up and your body is twisting slightly with a 3 point harness...your head will be closer than you think...not worth it...never will be.
If your fabric handles rotate on your bar...ATTACH them to the bar...don't install something that can kill you because it looks cool...just saying as I've seen so many grab handles that you can hit your head on without trying...