Vacuum Table

Anyone out there ever built a vacuum table for a cnc router? I am
in the process of building a new larger router and would like to add
a vacuum part hold down to it. I picked up a couple of vacuum pumps
at the NC State University surplus today although I am not sure if they
will work for it yet. They are nice units direct drive high vacuum lab
units. What I need to know is what size and number of holes would
I drill in a 4' X 4' table? I will probably add some valves to section
the table off, possibly go back and get another pump and section it
into thirds, one pump for each section. Use only the sections I need
to, depending on the size fo the work. I was thinking of using an acrylic
sheet maybe 3/4" thick for the table. Will it require a large O-Ring
around the edge or will just the holes be sufficent? Any tips would be
appreciated.

Thanks
Bill