12.1 Public Beta to 12.0

How do I downgrade from 12.1 to 12? I have an XS Max and am experiencing the poor signal issue. The suggestion I read was to do a restore, but I can't as long as I'm in the public beta, so I removed the profile, downloaded the IPSW file, and tried to do a manual restore on the phone in iTunes. No dice. Any suggestions are appreciated, other than wait for 12.1 to be official.