Hey Bob;
  If you come up with a date and title, I should have the mag. You might want to check out the 1/2A section, as Larry Renger did a write up on balloon tanks for 1/2As, and I wouldn't think it should be much different for a bigger engine. It was basically one balloon inside another, with a pick up line and a vent line. That's all I can remember. Goldberg Models used to sell a nylon bracket for Cox engines that adapted to the product engines with no mounting holes, and it included a balloon and some tubing.
   Type at you later,
  Dan McEntee

there u go Dan,  M/A april 2004,pg 159

think it has also been used in sport pylon racing

Bill u are right ,I remember it that way the bottle must be air tight