Suggestions

I want to make a new box. the one i have no is being smothered by my trunk ( its too big ) its a slot port right now for four 12s ( pioneer TS-W1207D2 ) 81sq inches. I want to go with flare port to make some more room in trunk and just for the ease of build. I don't know whether to go with one 6" flare or two 4". I'm thinking of dividing the subwoofers in two separate chambers ( two in each ) just to prevent the turbulence acting against each other. Just want to know some ideas