I haven't done it, but have seen where the trick is to start with the car on the ground, under the lift. You now have two strong rails running above over the length of the car, one on each side, suitable for infinite attachment points for lifting straps, chains, etc.
I lifted a boat off a trailer with mine so the bottom could be painted. Wish I had a picture. My 4 post is the Bendpak HD-9XW so it goes up 7 feet.





