vacuum hold down

I'm thinking of adding vacuum hold down to my 4'x4' router. I
would like to use a shop vac as this is low budget operation! My
current thought is to place some small 1/4" or so thick strips of
wood on top of my table. Level these off with the router and than
place a sheet of Polycarbonate over these strips and drill the
appropriate holes to hold down the work. Most of the work I do is
cut through stuff and I don't want to chew up my vacuum table
surface. Is there something that will let the vacuum through that I
can sacrafice? Or just replace the polycarbonate as needed? Or put
on a piece of sacraficial wood on top of the polycarbonate and drill
hole through this as well to get the vacuum where I need it?

Pretty new to this stuff! So any help is appreciated!