I just installed one, finished (99%) tonight so haven't had a chance to use it. Pallet rack posts are doubled on the inside for strength using flat bar.
best thing i ever put in my shop! it is not perfectly ideal with only a 9'6" ceiling height but it is so much better than a engine hoist. made mine from scratch from some 12" beams that i cut in half to make tee's out of so the flange sits against the wall web faces out.also mound my english wheel to one of the columns and a giant fans on another.gets used more than i ever would have imagined! also worked great when my son was 1 year old i could bring him in the shop in his jump up swing and bring him right were i was working!