I used the underground pipe extension mod but not for Py.
When I got niobium pipes the red extensions would not connect to niobium pipes so I downloaded this mod too.
Unfortunately the yellow extensions got one tile shorter, so my entire base is broken.
Is there a way to cheat one extra tile on the yellow extensions so that I don't have to rebuild all my piping?

This mod requires py to be installed so how did you use it without py? shouldn't you ask this question in the original AFH mod page?

You can check the mod's settings, there's an option there that can help you.

Ohh, I didn't explain properly.
There are the "Advanced Fluid Handling mod", and the "Advanced Fluid Handling mod for PyMods" (this mod)
I was always using py, but I had the "general" pipe extension mod, and it was working for py as far as niobium pipes. So in addition to the mod I had, I installed this too. Now the niobium pipes are connecting with red extensions but the yellow extensions is now one shorter. than the ones I had..

Ahh, I found in Mod settings -> Startup -> Make undergrounds longer by one tile.
Unfortunately I cannot check it now that the game has started.