Steps taken 1. Unitize all edges (rectangularise polygon does this alternatively) 2. Select seam and invert selection. then Weld Everything everything (rectangularise polygon does this alternatively) 3. Unfold with vertical/horizontal constraints depending on orientation (RizomUV unable to do very well)
RizomUV doesn't do a good job unfolding with horizontal/vertical constraints especially when all the edges are selected. I thought I'd do a request in adding a feature that UV Maps it like the video i linked earlier. Maybe add a special tab dedicated for Pipes with 2 buttons does all the steps and unfolds with constraints horizontally and the other button unfolds with constraints vertically.