I built a box for a guy a few months back for 2 CVR's. Did 3.5 cubes @ 35Hz. Couldn't fit a bigger box, but it sounded decent and got pretty loud. 4 - 4 1/2 cubes would be even better...
1996 chevy blazer 2 door so i can git really big theres not much space the biggest box i can fit would be 28x13.5x37 thats the out side dem of my sealed and its a tight fit
You can make it one common chamber or two different chambers. Just make that one chamber twice as big as you would for one. what kind of music do you listen to?