Can you post the code or describe the goal of the analysis?
I think I would extend the pipe lengths and add the next parts in the assy and fix them.
"A remote load on the top surface of the TEE (some moments and forces - blue symbol in the picture)"
Can you clarify teh moments and forces a bit further. Because then based on that I think I can help you. The trick with this in many cases is adding an extra feature to the part and restrain that feature. In such a way that it does not effect your analysis.
Thank you, that makes sense. I will give it a try.