I took a pretty bad spill this year at KoH without ratcheting belts in a hard shell seat with UPR cushion, and I was fine. That being said, I built the car and made sure that the belt mounts and routing were set up for me. I am smaller than most and have had issues in vehicles that I didn't set up. I am very conscious about making sure I am in tight every time. Any vehicle I get into, I make sure that the belts fit me correctly before we move anywhere. It is simply not worth the risk in my opinion. If that means I need to shorten the belts or change the routing that is what I will do. That being said, I will spring for ratcheting on my next set. I'd rather spend a little extra on safety than having that extra light bar or whatever else. Pull up versus pull down is another thing to look at. Where do the adjusters end up when you are strapped in, are they interfering with the seat or slots in the seat, etc. Also consider your neck restraint type and if the padded harnesses are better or worse for you.
You also have to consider the seat type. When I raced with suspension seats, I could never get tight enough. I'd be tight enough for a little while, but always had to readjust as the race went on. I will also never use a hard shell seat without my cushion. It cost almost $300 but my back didn't hurt at all after our wreck. Can't say the same for the driver. He was hurting for a while and went to the chiropractor multiple times.