I'm not sure this would be "legal" for a UIL competition or something similar, but how about making a couple of "half circle" forms from PVC pipe to slide through a fold-over hem at the top and bottom of the "tent"? They can be formed using 10 foot lengths, coupled if necessary, and heated with a heat gun (inexpensive at Harbor Freight Tools) before bending into the half circle shape.  If you know anyone with a pipe bender (professional electricians often have them) you could use 1 inch steel conduit instead.  Then it would be a simple matter to hang the half circle "tent" from whatever structure is above (fly system or steel supports).  If it all goes up to one single support rope (which would suggest a tent structure), but kept from spinning by anchoring the base with a sand bag or two, it would be simple to rotate it around so the "back" was now the "front" for your exterior scene.  This could even be done without anyone being seen moving it around from behind.  ...Clear as mud, huh?  Well, it's just a suggestion.  Good luck with whatever you try.