Why not just pay the extra luggage charge for the extra piece, it's usually not that much $$$. Some airlines are also a little laxed in their number of pieces, but that may have changes in recent years.When I was in Texas a couple of years back, Ibought a huge 3d target and they didn't charge me extra on the flight home. It was well oversized, and I already had two pieces checked in.

Anywayyour treestand can't be more then 25 pounds. I'd take it with you, check it in, and pay the extra fee if you have to.