Scrap all that.
I just realized I was using diameter as radius. Aaarrrggh.
So I get 98 lbs only.
Sorry!
No prob. I also explained below that part of the balloon was flat, meaning it wasnt even fill near capacity. The video showed the saucer slowly spin and you could see a nice flat sheet of the mylar canopy flapping around and behind the rest of the balloon. This thing was designed to lift no more than 8-15 lbs total in equipment. I have no idea what he was going to use it for, but it could certainly lift a small GPS unit, digital camera, altimeter, etc. Small stuff to take measurements and stuff. Not a 40 pound payload,let alone how much the canopy and balloon weighed.