Do NOT use a bracket for hanging a car. It can get you hurt or killed. Those brackets are for preventing car movement when its still roped up etc, like your adjusting a brake.
Adjusting tensions, im not sure on the 3300s If you can see Individual load cell info or not. The gen 2s all shackles are on springs. I adjusted till even tension compressed springs evenly. Felt by hand, was good as far as I can tell. Normally I would use a real tension gauge on ropes to verify each rope one at a time. Just another fun thing you can't do with belts.
The Otis belts have pretty much zero constructional stretch, I'd imagine the schindlers are the same. Verify before roping, if you stay up closer to your max cwt run by you shouldn't have to ever shorten them
