Summary

I wanted metal fittings, so I slapped some primitives on the STL and glued in some hastily machined bits of scrap metal. Included is the original STL, the SCAD file, and the STL that I used for my particular fitting sizes. This is probably useless unless you configure it for the sizes of what you have.

I'm inclined to suggest that the printed assembly should be coated to reduce permeability. I have no good way to test the permeability of this part, but basically everything else I've printed has leaked vacuum like a sponge unless it was coated.