Help lost in box figures

[dog24fret]

I'm building my fourth box but this one will be ported. I wasn't able to load my box plans up but I'll describe it the best I can. First it is going in a 97 ford e150. I'll be running 6 12" hifonics hifi. They will be powered by 2 DD cm1 amps, 3 subs per amp at 2ohms. The box measurements are as follows 33"h,45"w,21"d with a divider in-between the three on top and the three on bottom. I'm wanting to put a square port in the upper and lower chambers hopefully tuned at 36-37hz if possible. The figures I have so far is 15.46 ft3 total volume and 7.71 ft3 for the two cambers. Now I'm lost I don't know how to figure out the displacement for the subs. I also don't know a thing about square ports so I have no clue to length ,size or displacement. I've tried to use t box wizards and got even more confused. The local shop has a new box builder that say he just graduated from a install school. He told me I'm over figureing that there is no need for all this calculating. That all I need to do is put the subs in and make the ports on the side 3" wide and 4" from the back straight down. That it will hit hard and still sound good with all music and my worries about loss of cone control is overrated. Please help me with this as I want it as close to right as I can get. I would like something between hard hitting bass to good response to kick bass in rock with what I have.

[dog24fret]

Could someone help me with this cause I don't want to screw it up. First ported box build I've done. I need to know what the port size and lenth will be. If I explained everything right if not correct me. I'll be starting the box tomorrow if possible.