Not necessarily, less felt could equal more reflections causing cancellation == less bass, but I could see it going either way. I would definitely try swapping the drivers if you want a definitive answer. But that might entail cutting the wires, so filling in the gap might actually be easier. If you're talking about being really really picky, (a) well hell, you're in the right place now, then, aren't you? ( ...that would make a really really picky bit of difference, so the scale of problem to solution is right.