I think you're creating problems where they don't exist. I've never known anyone who broke a high back on the lift. I guess sometimes shit happens, but this has never been a concern to me. Leave em up or fold em down. Shouldn't make a difference. I leave em up. Except for first chair since they were already folded down for the drive to the hill.
Sooner or later some 250 lb skier will sit down on one end of the chair before everyone else. If you're beside that dude he will tilt the lift down and crush your highback. Always fold.