I actually took the filter off the little shopvac before doing this…specifically because I figured I didn’t need it and less restriction would be better. I just didn’t realize there was that horrible clogged up filter inside the housing 
I actually have a vacuum pump I use for servicing my car/truck AC…but…I don’t know that it’s could pump down this much volume efficiently. I may try it…just going to take more custom fittings than I wanted to deal with to try. It’s actually a little quieter than the shop vac too so it’s got that going for it.
Apparently dust collectors aren’t great for this. The issue is they have lower static pressure and are designed more to move a high volume of air, for a vac table you want the opposite, high static pressure with less volume. But I have seen a few who did get them working.
I suspect the reason a lot of people don’t need to add leakage is that they use porous MDF to build the vac table so they have some “built in” leakage. But a lot of CNC forums also claim that shopvac’s don’t make enough vacuum for “real” CNC work. But I’d say it depends on what you’re doing.
If you’re working on small metal parts you don’t have as much surface area but you need a lot of holding strength so you need higher vacuum. For me working on big sheets of foam…I’ve got tons of surface area and not a lot of force against my work - so I can get by with pretty minimal vacuum.
That said…I do have it sucking itself to the particle board base so I expected there to be some leakage from that. And with the extra leakage hole I added I still can’t move my work and get great cuts. But…it’s definitely not as strong as I can pull the board up to reposition it MUCH easier.
I think I saw those $25 vacs the donek guy uses at wallmart the other day - so I’m going to check that out. I still suspect the big issue is my vac was old and abused and tired. And $25 is cheap enough to almost be disposable if I can get a year or so of use out of it.
I actually also have a blower fan I just took off my car and replaced…before I even started this project I was toying with making a housing for it and seeing if it could create enough static pressure to work. Should be much quieter and it’s got a port that leaks cooling air to the motor. Might be a fun project to try just for kicks. But would increate my 12v load so I’d probably have to add another power supply 