2-memphis M3 12's 150db+

i have a 99 mustang that i am currently building. i have a panasonic 7300u indash(sucks for audio adjustment), 2 pr of memphis mclass sq6.5 component sets, 2 memphis m class 300's, a memphis mclass 1000d, and 2 memphis m3 12's. i have built 3 boxes already trying to reach my goal of breaking 150 in the mustang with 2 12's. my last box that was built put me at 149.5 on the dash but the box was loading up and the voice coils would heat up after one sweep. we got back on the computer and decided that cutting the port down would allow better spl and solve the voice coil problem, but i actually went down on spl to a 144.2 on the dash and lost out on regular music. i am trying to keep the car's ability to play normal music intact but now it only likes 50hz. currently the box that i have is 7.2 ft3 with a 16in x 4in x 4in rectangle port. the 149.5 came from the same box but the port was 13.5 x 4 x 20.25. i need to know if anyone out there is working with box designs on the memphis m3's and what they have found to work because we have spent hours on the computer trying to design a box and nothing seems to work. i found one but it required around 10ft3 and it still wasnt that great. im trying not to build a wall. i took out the back seats and cut around the opening and am using the slant of where the seat was as the front of my box going back into the trunk. im trying to find out if anyone else has been trying to use these subs and if so what kind of luck they have had and what style of enclosure have they found to be best. any help that you could offer would be great since i have a car show coming up on july 4th that everyone is expecting me to be entering since i have the hardest hitting pair of 12's around but i wont enter if im not satisfied and over 150db. thanks

 

is there anyone out there who has any info that they could possible give me on some other applications of this equipment.