Trying to design a custom enclosure

I have a 1998 Mercury Mountaineer. I currently have a loaded sledgehammer enclosure with two thunder 7500's. This box sounds incredible but I need something that fits my truck a little better. I have a design in my head but it's kind of complex and I'm not sure how to build it to meet the airspace requirements so I thought I would ask for a little help. I know this may seem easy for some but I never have been very good at things like this so please be kind :P. anyway I have the measurements that cannot be changed and the basic shape of the box I am having problems figuring out the missing measurements.

This is the basic layout.

In the front view the cutout is for the wheel well behind the backseat and in the side view the bottom part would be between the wheel wells. actually I'm going to build two seprate boxes and hopefully have 17" between them for a custom amp rack for my two kicker amps. The full width above the wheel wells I have to work with is 52" and the width between the wheel wells themselves is 41.5 inches I will be building the enclose using .75' MDF and covering it with vinyl. The subwoofer specs call for aprox. 2 cubic feet of airspace for a ported enclosure. I know this seems like I'm trying to get some one to do the work for me but believe me when I say I have been working on this for weeks and to be honest end up getting confused and short tempered. Any help on this would be appreciated.

Give us a couple of days... we'll see what we can do for you, but we would like to know how deep we can make the enclosure, just in case. And second, does the area behind the speaker have to be beveled? if we can make it vertical it will give us a little bit more airspace.

Our preliminary look at the information may require us to reformat the look to get clean sound and give you the space needed between them.

Also, our guy wants to know if he can go under the seats too. If so, then how high is it under the seats and how deep can he go? (well... you go.)

Lastly, if you do not mind, please take a picture of the area you want to install it in and post it up. It would make it a lot easier to see what area we have to work with.

Sorry it took so long to reply, Things have been crazy at work lately. Anyway this will be going into the cargo area of a 1998 Mountaineer (ford explorer) so there is now underseat and I have to keep my back seat. I want to keep the depth as shallow as possibel but I can do with out a ported box if that would make it easier. I would do this out of fiberglass but I am not very comfortable with my fiberglassing skills yet and plan on showing this truck a little this summer locally. Here is a pic with what I had in the back of it a while ago but have since upgraded my equipment and should give you a pretty good idea of space...

Any help at all would be awsome as I really want to get the box and amp rack built and in asap

I wouldn't worry about it anymore. I appreciate your help but some stuff recently happened and looks like I may be building a custome fg enclosure to fit 4-6 12"s in it. I do thank you though for taking the time to look at this for me.