The "Model Tree" was shown on SSW (?) by Mitch from Tulsa. He's not on the forums anymore, but I hope he's still building and flying. I have some text from him, maybe answer to a PM or post, not sure. But it looks good to me, and makes good use of those room corners.

Steve
"No problem at all with open bays. The plane tree is built with two vertical 2x4s and three 1x4s running horizontal, making a ladder. The horizontals are held in place with metal angle pieces and covered with foam to protect any tail that might come in contact with them. The base is two 2x4s bolted 90 degrees to the uprights. The arms are 1x2 drilled with four staggered bolts through the 2x4s. Also covered with split foam. All wood stained. De built this very strong and it is extremely practical and I love it. I need another, but I keep smashing planes, so it would never fill up. Mitch"