Gregg,
The only elk decoy that's going to do you any good is one that is easy enough to carry that you don't think about it when you pack it. That said, I've found the Montana cow elk decoy which looks like the rear end only of the cow is the most compact. Forget the legs and make a loop of twine or fishing line at the top and hang it over a branch. Set it about 30 yards behind you and to the upwind side if possible. Sometimes you forget you've put the decoy out and it kind of scares you when you look back and think an elk has snuck in on you! Also the decoy has to be where the bull can see it from the 75-100 yard range, which I find is where they first hang up to the call and want a visual confirmation before they commit.