I'm making a second attempt at a vacuum table top.
I have 3/4" plywood as my base, and 1"x2" will be used to frame it in and provide spacers in between the base and the top. All wood has been sealed with KILZ water base primer and I'll be putting a water based clear over that. I have drilled a hole near the center of the base sheet and used bathroom caulk to seal around a PVC pipe which connects to a shop vac.

The top sheet is what I'm wondering about.
Would it be better to use another sheet of 3/4" plywood, and then have the shopbot drill hundreds of small holes in it (I'm thinking approx. 2" apart) or would it be just as good to put on a sheet of 1/2" or 3/4" particle board without having to drill any holes?

After deciding on plywood with holes, or particle board with no holes, I was going to place a sheet of 1/8" or 1/4" sacrificial masonite on top,seal all my edges with duct tape and turn it on.

I'm having doubts if a shop vac will be able to pull enough vacuum through a sheet of particle board to hold anything down. My shop vac is a 3.25 peak HP, with a 16 gal tank.

Incidently, none of the local lumber yards seem to have anything they call LDF, which I have seen mentioned here in the past. Or is that the same as particle board?

I appreciate any comments and advice.