Ok I got it. I'm an idiot. My problem was that I was creating backup copies of the model files IN the models folder and the game was choosing them to use.
So you can have a file named like:
22CMNColumbiad-MYCOOLCHANGES.mdl and it will still find it, lol, just make sure it's the only one in there with the key prefix "22CMNColumbiad".
So looks like now I get to use field artillery replacement chits for Parrot/Columbiads