Hot Tub adapter

A work in progress for discussion amongst collegues.
The long range project is to heat the MSpa hot tub from a remote heat source.
This is the first step in figuring out the plumbing fittings. I found a jet Nozzle here :
https://www.thingiverse.com/thing:3122220 by https://www.thingiverse.com/fransm.
I imported it into FreeCad, did the mesh conversion and subtracted what I needed to to create a threaded flange. I then created a matching negative space Nut to make a sealed fitting. Next step will probably be adding a hose barb to connect to external heat source.
Yes I could have figured out how to do threads, but this was more in my skill set.
I left each of the steps in the FreeCad file so that you could follow the steps from importing the original STL to the new STL.

Photo's included are : The original MSpa flange and The first cut of the found jet listed above that provided the thread for threading the original flange into.

Just printing first test in PLA will likely pr