Vacuum Gaps

I have a question for Gary Weaver here

In a post of yours dated 4-9-00, you were talking about your vacuum static 
gap.  I am currently using an async rotary but I have a spare RQ gap laying 
around that I plan to modify as you have described.  It currently is open on 
the bottom with a muffin fan on top.  As is, this gap would not quench with 
my 5kva pole transformer.  I plan to seal the bottom and cut slots in the 
sides between the gap sections.  Then install a new end cap on top with 
fitting for an air hose to the vacuum motor.  How much air am I going to have 
to move through the gaps?  What do you use for a vacuum source?  You mention 
adjusting the air flow with a variac for best performance.  Can you get too 
much air flow at this power level?

Thanks, Ed Sonderman