I built mine..
I was not that hard....
I purchased most of he stuff from Mike at botlifts.com
the only problem I had was off setting the pull hoist bar so the tower would miss it....
We have a two story boat house and I wanted to lift the boat as high as possible so that gear could be loaded and off loaded into storage room on second floor.. Works like a charm.
When I off set the hoist it added extra tension to the pullys on the other side of the boat. so I added a 4" flat bar all the way across the beams in the boat house.