Lee Einer wrote: > So, any advice on how to keep the buckets from collapsing?
I think you're pulling a "harder" vacuum than is really necessary. You might create a controllable leak somehow to bleed in some air. A 6 hp shop vac is pretty powerful. It doesn't take nearly as much suction as you'd imagine. The commercial, hand-pumped Topsider I have uses a steel 5-gallon gasoline can, the domed kind. The dome makes it very strong as long as you don't lean on it while vacuum is applied (which risks causing the dome to "snap through.")
