Like I said earlier, I'm not a big fan of window film, but it could be a good choice here. My big gripe has to do with it's flimsiness and the difficulty of keeping it in one place after you lay it down. There are stick on Tyvek tieouts available that might work well with the window film. Tyvek Tape might be a good edge reinforcement. The biggest piece of window film that I recall seeing in the stores was around 5' X 7'. That's not enough for a single piece footprint in a big tent. It may well be available in bigger pieces, but I haven't seen them. It might be possible to join two pieces with the tape that comes with the film. You'd need a big table to stretch the film out on to make the seam. I'd like to have an 8' X 9' piece, if I could find one, but I haven't looked very hard, yet.