So, I gave up on the idea of continuing to use the centerline of my pipe (civil 3d pipe networks), set with a width of the inner wall of my pipe, since it won't properly trim at the structure, even though it trims the out/inside walls accordingly. I've now been trying to create a hatch that will mimic the Hidden linetype, but I've never created a custom hatch pattern and it's proving to be a bit over my head.