It's generally not practical to fabricate a shoe with a narrow slope, but it is practical to increase the height of the shoe as the pipe gets farther away from the starting elevation.

Assuming you go flat:

For stress purposes, assume that your stresses are under-representing the fact that shoes are sitting flat on steel.

How much? Run a test. Route 5 straight spans (no slope is ok), and instead of supports, use displacements. 0" in the vertical and 1% slope's equivalent rotation at each support.

Run a WNC and WNC+D1 case. While it's not fully accurate, but it'll at least get you into the ballpark as to what it does to your pipe.

Assuming you go rod, I do expect there will be a net force of a long line moving from the high end to the low end, especially if your pipe is rigid, and your spans are too short.

The more stiff the pipe, the closer the supports are, the closer this approaches to a solid object sitting on a solid incline.

However, the less stiff the pipe, the further apart the supports are, the closer this approaches a catenary powerline. Powerlines don't slide downhill, after all.

As usual, it's not one-size fits all, and that's not to say the solid object on the solid incline effect isn't acceptable - it just means more loads on the low end, that may or may not be acceptable and addressable.