vacuum gasket for custom PCB exposure press

[coppercone2]

What is a good material that can be used to make a PCB exposure press? The PCB would have a thickness of 1.6mm, with 2x translucency (i assume something like 0.3mm).

I just want to sandwich plexiglass to some kind of base (aluminum?) with a vacuum pump.

Would 2mm silicone sheet work? Can you determine the thickness of a gasket you could use to make a sandwich seal on something based on its thickness and durometer?

Is there a better solution then cutting a whole gasket out of a single sheet, like strips you can glue together? (like something in a vacuum sealer). I thought to maybe just cut silicone tubing in half, fill it with silicone adhesive, then press it between two plates with a 2mm spacer (hopefully it would deform by 1/2 a mm under vacuum but I am not sure)