I just tested this to confirm, with the radio in GMRS mode, it doesn't matter what you do in Chirp to channels 8-14. I turned off TX disable. I changed power level, also tried changing the TX frequency to that of Chan 1 (462.5625). The radio refuses to TX on those channel numbers. It's locked in firmware and Chirp doesn't allow you to bypass it. ofc if you change the radio mode out of GMRS then you can do what you want.