The Civic did 142.9 dB, twice within 5 minutes. All is well, also got the tuning right. After that we cut another speaker hole and went with a normal alignment. No more bottoming out, all that the Steg 800w @ 4 ohms amp could do, the little buggers took it and put up 142.8 dB. It's 0.1 less than the isobaric alignment, with more power. If they survive thermally they are going to be ok, I have a feeling that bumping the tuning higher will get us over 143.0 in the Civic. Next step is bracing, then doubling up the bottom of the box and the baffle. Bracing is not appealing, I've had mixed results but who knows what's going to happen considering the box is made out of particle board.