FWIW, I picked up a couple cheap, plastic fuel filters today, and will look
through my TIG and plasma parts to see if I can find a suitable restriction
to go along with it.  

Interestingly, I told the auto parts guy what I was doing, and it turns out
that he used to work for a company that made, and serviced blood gas
analyzers.  He said they are all based on pneumatic operation, and employed
accumulators, and "chokes" (his word for the restrictor).  He said he used
to carry a box of various chokes to fine tune the systems.

Not sure when I'll get to test it, but maybe this weekend, if I quit putting
off the fiberglassing chore.

Rusty