After more thought, I'm not going to complete THR until later as well. This comes from my desire to consolidate projects so I can focus on other more important ones.
The water gun itself is nearly done aside from the PC and cementing. Performance depends solely on the PC so I don't think any testing is necessary. There are also many things I'd change in a future design so THR has already served its purposes as a test for a good way to have a built in reservoir.
Some sort of guide will be in the works probably for a while. It's not mission critical obviously but at least a page about how we got the pipes to fit in the plastic with a router would help many people.