Guys...
A few notes on this system. Now that I have built, sold and installed a number of these systems, Most are being switched to full manual control.

Reasons are:
1) cost (saves a few hundred $)
2) I have noticed on mine that the vacuum varies much more than I originally thought. From a freshly surfaced spoilboard to 25 sheets into a job I may have almost 2 inHg difference. This moving target of initial vacuum made the hysteresis settings a real pain. In the end, sheets were initially cut with 2 motors and 4 are used to add hold down for the cut thru.

I was hoping to automate this switching, but it appears that either another approach to the control or full manual is the answer.