I am helping a friend of mine setup a vacuum system on a Shopbot that he is in charge of at a local college. We are going to make the plenum out of standard MDF with 6 zones. Then glue down a 3/4" thick piece of Trupan for the bleeder board.

I've had my own Shopbot many years without a vacuum table, so I am new to vacuum systems and I am accustomed to screwing everything down. Is it heresy to use screws to hold down small irregular pieces that don't go all the way through the bleeder board?

I know you can use a sacrificial piece of plywood and screw to that and hold with the vacuum. But, I just wondered if your could screw into your bleeder board without ill effects in order to save turning on the vacuum for small jobs.