Just got my 18" Q w/BP in the mail yesterday. (thx scott). Next week is spring break and I need a box design for the back of a 97 blazer. I have about 8 cubes to work with. Accordman from steavemeadeforums told me to go 6.3 ft^3 and 90 in^3 of port, which results in a 32-33 hz tuning. I have never worked with 18's before, and I've heard certain boxes for 18" Q's can really restrict their output. I only have about 1000 watts RMS from a bxi1206d to work with for now, but plan on upgrading to 1400watts rms. My goal is to make a well balanced box. Not pure SPL or superlow tuning for SQ. I just want to get the most, good sounding output from the sub. And i'm a broke ass college student so I can't afford to play around with different boxes, i wanna hit it on the money first time. here is a quick sketch i did. Top will be double baffle, and I will add some form of bracing. nothing is to scale, just a quick sketch to show you what design I plan on using.