I have been having a small problem when I surface my top and then go to cut some thing it would cut through at spots but not at other places. I happened to throw sheet on and started the vac I saw that my bleeder board sucked down in places. I ended up using a flat bar to see how much it moved and noticed that the glue wasn't holding do to the plenum to my table base. I ended up removing that plenum and cutting a new one from 25 mm PVC and screwing it to the table top put on a new spoil board and surfaced it. Boy what a difference that made now every thing stays level