I just set up my bow and made the stand. I've toyed with the idea of making a canopy and the only thing that I can come up with is to make a stand in reverse. Rather than have the top open, have two doors in the front to allow access. The only problem that I se is that there would be a lot of waste because of the bow from 12 to 18" should be one solid piece. If made of Oak that's $45 for just that one piece.
Let me know if you make one.