Mark, I don`t have a problem with your metisse, the bike is eligible to be race in pre 65, I have no delt that the maico where built in 64, Mark your taking it out of contexts.
The very first bultaco metisse was a single down tube side port 200cc 4 speed, what these companies like montesa and bultaco did, they started off building small capacity engine and build up to 250 and larger capacity. I am not knocking your bike, its a lovely bike as I said before.
Yes, I do want people to build these bikes, because pre 65 is great class and true era and they must strick to rules, if a person is building a pre 65 race bike, as long as they do it right, in your defence mark, your bike is fine.