I always thought the foam port plugs on a SVS PB12+2 would be compressed and held in by the port, but on my PB12+2 the foam plugs are loosely setting inside the port. I seems like they could be accidentally bumped (or pushed in by a small kid) and fall inside the enclosure. Is this the way it is supposed to be, and the way it is on all PB12+2s? The port plugs apparently don’t need to be tight fitting to function properly? Any insight?