Well I decided to ditch my dual 12 set up and go for a single 18 DC Level 4 XL in the back. I've been playing around with designs for the past week and finally settled on something. I went to Menards yesterday, got two sheet of MDF and went to work today. It's 6 cubes tuned to 36hz. After my Ebay sale is done on Sunday I'll order the 18 Monday, then I'm going to wait to attach the second baffle until I can make sure it fits good with the sub, and then come a little testing and Herculiner after I'm happy with everything.