Not a problem as the others said. None of the PAMPA classes require BOM. You can fly anything, you just give up Appearance Points if you didn't build it in Intermediate, Advanced, and Expert. Beginner does not have Appearance Points, even at the NATS, where it's an "unofficial event".
BOM is only required in the Age Group competitions at the NATS. There are bought/donated planes flying at every contest around I would bet, and ARFs/ARCs, too.
it's interesting that Jack Sheeks, back in the '60s, threw out the question of dropping BOM for Juniors in an article on one of his *thousand* published planes! Seems Junior participation (pre-PAMPA) was dropping off.

Bill <><