This sounds like something that I would have to do, so here are my thoughts:
I like the
PVC pipe idea, but you need to
bend it, which takes heat and care. With a 6’ diameter and 7’ height, you are right at the limit of standard 10’ lengths of
PVC. I don’t know what a “good”
spacing will be for the vertical bars, but at 1’, you’ll need about 20. If you heat and
bend the
PVC pipe, you can cut a form out of plywood so that you can
bend them all the same shape/curve. (You should be able to find instructions for heating and bending
PVC in a
theatre craft
book.)
(The top where these all come together will take some thought, considering that you need to take this apart and put it back together at the venues. [perhaps a circle of plywood with PVC couplings attached along the radii.] I think there will also need to be some horizontal support (or hoop). Maybe flexible polyethylene pipe, but I can’t think of a fast assembly/disassembly method).
If the bottom/
platform needs to be functional (that is, support a dancer or two), it may end up weighing in excess of 100 lb. (You mentioned that lifting might be issue.)
(The pipe in this post refers to schedule 40
PVC pipe.)
Joe