Does anyone have experience making a vacuum press flip-top frame table? I am making one without plans using standard t-slotted framing from McMaster Carr. I have used a vacuum press before that was made from a kit. The Polyurethane membrane used on the kits has a 6" box joint formed into the membrane. The membrane that I have is a flat sheet. I'm having trouble cleanly attaching the membrane at the corners to the t-slotted frame. The best I have come up with is a sloppy darted box joint like wrapping a present. is it possible to form the corners? I'm afraid I have already ruined the membrane.