need help designing my blow thru enclosure for my truck

ok my problem is that i built a ported box like in the pic for 3 cheap 15" subs like really cheap just so i could use all the 1000 watts and alot of cone space. but then i wanted to put it in the canopy of my truck and have it blow thru into my truck cab.....so i put the boot on my canopy and built a box over the face so that the sound would be directed into the cab of my truck....but because i put the cap/box/port thing on the front of the box there is bass cancelation and idk how to tune it......if anyone can think of a better set up that will do the same job i will do it! haha