It would be very rare for anybody to question it at a club level race and if they do, find some new people to sail with.
A regional regatta that is class sponsored will not allow it.
The one exception would be if you came in as a new guy and suddenly win a few races in a row, somebody will bust your balls about the non-legal boat.
Have to agree with Eddie.
Perhaps there's a club in your neck of the woods that has 'Portsmouth handicap' racing.
I occasionally race on a tiny lake with a Laser II, a Laser, a Vanguard 15 and several Sunfish. We do have a very nice lady who times us all as we cross the finish line.