Frank, this one is for you. I spent part of the day crawling around in the back of our Jimmy installing the amp, sub, and 6x9 in the new side panels, which, thanks to you look great. I did a little measuring while I was back there and came up with the following: CU ft of air space behind the rear side panels on my '90 Jimmy is aproximately 1.98. Don't take that to the bank, but it should be close. When I get the panels carpeted I will post my pics.