I have personally had great luck with series 6ths in vehicles with no deadener, no nothing, just a wall. They always seem to perform well, because that front chamber is keeping the subs balanced, where the flexing of the vehicle isn't directly affecting the front wave/sub cone movement, since there's the buffer of the front chamber pressure and port. So, it seems to really help the sub still move properly, and make tons of pressure out of that front port, regardless of the shape of the vehicle. I have some Tahoe-Suburban buddies I design a lot for, or have, and uhhhhh......their vehicles need help......lol. They mostly run 6th's and don't wanna run anything else, due to the control-ability of a series 6th on the sub itself, with both front and rear wave control; it's full power extraction, IMO.