Frustrated With all these limitations!!!

[36jere]

Good afternoon , I need some help with this box I'm designing/ trying to. I'm by far not the best box maker in the world but I've made I don't know 15 boxes probably my time just never one that had so many limitations this is going in my Dodge Challenger Scat pack going into the trunk facing forward woofer forward port forward . Box can only be 15 and 1/2 inches tall the width on the bottom is 31 1/2 Max but when you go up 3 in from bottom of box I can expand that to 36 1/2" as far as depth goes I only have 20 in Max and that's because I have all my amps and stuff in the spare tire area underneath the bottom floor and in order to access that I have to have that box 20 inches if not I have to take the whole box out to  adjust anything . I'm looking for 4.25 ft3 or bigger but I realize that's just not possible. I'd like at least 60 inches of port area I like to tune about 32 Hertz it is for a Sundown Audio X-15 V2 by the way just one. Currently I'm running about 500 watts RMS 1000 maximum RMS upgrade in the future is possible. Any input would greatly be appreciated. Double baffled and using .75 mdf. If I forgot anything let me know. Thk