Have you followed the setup procedure in the manual?
Is it a quick attach loader frame? And if so, when you say you are measuring the frame, are you measuring the part that gets removed, or the part bolted to the tractor?
If the part bolted to the tractor is off, I think adjusting air pressure might be the only solution.
I thought about that after the fact. The fellow hasn't been successful getting the bucket level by loosening the loader frame, so I'm not pursuing it any further.It's probably got a slight twist in the arms, is it hard to get on and off the tractor? If you buy, check that first.