I'd tend to agree with Bob, as scary as that is. Think of it this way. If you simply sealed a single sheet of plastic bag material around the edge of a 500 square inch table and pulled a 6hg vacuum, you'd have approximately 1500 lbs. Why and how would the same 6hg double just because the bag is on both sides? I suppose if you vacuumed a cube to 6hg with 500 square inch sides, it would be like using 9000 lbs?
GS