M.F.
Yes the hula hoop works for circular canopy's. You can also use the foam pool noodles if you are looking for a specific shape. The metal curtain rods can be used also. Just nothing heavy. I am a seamstress and have made all kinds of unique things for my kids over the years. If you want you can e-mail me and I will be more than happy to walk you through it. Good luck.
M.