Well, ran some tests today. Overall, I'm pleased with how this is progressing, but admittedly there is a problem that keeps nagging at my project. No matter how much helium I put in the balloons, or how big a balloon I purchase, they never have enough to do what I need them to. Helium is supposed to lift 1 pound per 15 cubic feet. Well, I put 30 cubic feet into a 200 gram balloon and it can't even pick up the camera BY ITSELF. It did manage to pick up the styrofoam container and gps phone by themselves, but not the camera....best I could muster was to attach my cellphone camera and let it fly on a tether. Well, it went up maybe 100 feet or so, and of course it brings another problem to light. The camera spins around so fast you can rarely tell what is going on. I did anticipate this, however, and plan on attaching the platform in such a way as to keep spinning to a minimum.
I'm learning that to do this right and with a reasonable guarantee of success it is taking a lot of work and experimentation. I'll get this figured out, one step at a time.