The cellular modem chipset might have some intelligence to detect timestamps on the firmware and never allow a downgrade. I tried the --cmt-no-verify flag and it didn't do anything. I've tried everything short of hex editing the old cmt file to make it appear newer to the phone (if that's even possible). I tested incoming/outgoing calls, sms, data and all work with the 1.2 file. IMO it's low risk compared to running on a full leaked 1.2 rootfs and all.