I'm in the same boat. I use a vertical lifting clamp, and my 2-ton engine hoist. I store the 4x8 sheets vertically on a rack, very similar to this:
[ATTACH=CONFIG]517[/ATTACH]
I lift the sheet up, roll the rack out from under it, and roll the engine hoist over to my table. With the engine hoist chain shortened a few lengths, the plate will swing up over my table. When letting the sheet down, I have to push the bottom of the sheet away from the lift. I don't have 4' between the boom and the cylinder, so the sheet will bind it up if I pull the bottom into the hoist.
I am also making up an assembly like this, for horizontal lifting. I think it will be quite handy.
[ATTACH=CONFIG]518[/ATTACH]
http://plasmaspider.com/viewtopic.php?f=3&t=17452&hilit=Engine+hoist