[BoomieMCT]

I agree - using an active crossover to prototype kinda sped stuff up a bit. I don't see what the big deal about padding woofers is though - I've seen other designs that do it. As an option you can pad them like the DDRs which are padded in a such a way that it provides some EQing to boost the low end. Or you could get by using smaller woofers. Or, as a third option, try using more sensitive mids. Since you are raising your lower crossover you can try using a 3" mid that doesn't have quite the bass or excursion of the B3N's. If the Tang Band W3-1364S's I lent you don't work there are a plethora of other options to consider. With 20 watts on each they shouldn't hit overexcursion above 450Hz.

Before my wife needs her amp and crossover back we need to try adding some angle brackets or something to that test baffle to make sure the woofers aren't loosing some energy moving the baffle instead of the air. I had something similar on my dipoles at about 150Hz before I added more bracing. Once that front baffle is stiff enough we can try messing with the size using cardboard or something.