What can go wrong flashing a modem file from another s6 variant?

I have a USCC Galaxy S6 (SM-G920R4), and all of the ROMs here don't have any support for it as far as I know. I was able to flash XtreStoLite and everything was working fine with the exception of the mobile data and voice. Is it possible to flash a modem from another device to get this to work? What are some options for getting the mobile data and voice to work?