There was some discussion about a trailer mounted boat lifting system:
http://boatstands.com/product/trailer-mounted-boat-lift/
Looked pretty good, but when I checked into it, you really needed to have a boat with a hard chine for it to work. I was thinking, why don't they have a similar system with a strap between the two lifts for sailboats. I called the company, and they said they are currently working on this and will have it out next year! Stay tuned.
Rib