It looks like MainSt_Per could just be MainSt on US 221 only. There are no other MainSt labels on that route unlike on US 19 and US 27.
I mainly just copied and pasted from the US-19 file there, and kinda just want to keep the routes labels synced along multiplexes. Mainly to avoid any future problems in case of other reroutes.
I wish that there was a better option for US19/98_Per, but I cannot think of one. (EDIT: Would using US19_S be feasible?)
Yeah, I was debating about this label for awhile myself. At first, I thought of making it US19/98_N and the southern one as US19/98_S, but didn't want to make people think there was a multiplex there. I could maybe make it 'US19/27Alt' instead, due to US-27Alt ending at that intersection. That's about the only other label I think would be feasible there to be honest.