Yup ! I did that as well. thought it was great...........
until you come across a curve pipe, Then as the flow arrow spans from BC to EC (chord bearing) my inverts do not align with my pipe at the manholes.
And that's not all....if you have a null structure, you get inverts that are not needed.
So ........ I am now in canoe with out a paddle, doing downstream.
…..fast