CAR 507.03(6)(c) Remember, putting it into O-M is a Canadian thing. It "becomes" a different model. Trucking it back over the border doesn't change it back.

Even the Canadian owner can't change it back with out the overhauls. CAR 507.02(3)(a) Has to be done by an approved shop too - no field overhauls.

Realistically, a helpful person at FAA can look at the regs and what happened and try to reverse the dataplate issue. Problem is, the FAA wants nothing to do with O-M planes and wish they didn't exist. As well, when was the last time anyone was helpful at the FAA?