I didn't save it when I added the support edges, that is why they aren't in this SS, but this is the normal map that it generated with the support edges.
Hi! Maybe I didn't word it right: Yes, border edges are looking straight, but the vertices on the edge are not distributed evenly. Split the corners like so to avoid UVs stretching:
and if I layer brushstrokes near the edges, it will warp the edges, which is kind of difficult to watch for... wondering if there was a better way to do this