That does make sense Geoffrey, the addition of a gasket was also something I was thinking about but was worried about the rubber/foam/cork getting damaged as I slide the sheets on and off the bed machine. I think a holding sheet will definitely reduce the need for a large pump and give me decent hold down.

Tabs are not an option as I plan to cut almost all the sheet material away so I am left with sawdust and parts :) Hence why I was thinking about painting the holding sheet as the surface area exposed will be quite large.