Sourcing the Venturis, Pumps, and impellers is only a consideration of convenience. Won't do much good to supply a simple process, if the parts themselves are exotic.

I'm focusing on the gas intake for now. As far as constriction goes you can actually go from a 5/8" barb to a 3/4" npt venturi and still supply adequate pressure if the gas intake is appropriately sized. So far this has been the simplest application with my Eheim 2217 canister.

Mazzei's drop in ports do go down to sufficiently small sizes, and only cost $2.50 USD, but the cap tubes work really well, and If I can cut these with a laser, labor is trivial, and 300 tubes will cost $6.70 USD, and the 1/8" bulkheads are $2.25 USD.

While I prefer the Mazzei injectors folks can buy the Venturi of their choosing screw in the metered bulkhead, and adjust the Co2 flow rate until their tank looks like a glass of Club Soda ! LOL. If it's stupid and it works, is it still stupid ??? Grtz, Prof M