I'm going to build a custom fiberglass sub enclosure (my current 3/4" MDF box weighs a tonn and takes up the whole trunk, 2-12") and I'm not exactly sure what I want to do. I was wondering if you guys could send me some pics to give me some ideas.

I have the same problem. My sub box takes up most of my hatch and I had to take the hatch cover out because it would hit the box.

I have seen a few custom boxes in this club but they have all been the kind that take up the entire hatch.

I'm trying to fit 4 15" subs in my car lol.... what I am planning on doing is angling them in all the corners... I know the side near the tail lights flaires out that little bit, although I have no pics Im sure you can squeeze a 12 in each corner and still keep alot of room.
Other possible option, both of em side by side right up against the backseats I think it's 15" from the floor of the trunk to the top of the seat.

Check out this picture.. maybe it is something you would consider... that way you get to keep your trunk. These are 2x12's

Hey Tim that looks pretty sweet, did ya do it yourself or have a shop build it. I actually thought of doing something like that, but with some type of cover that I can put over it, to stop people from seeing what I have for a system.

Hey Kyle, I don't think there is any posibble way to fit 4 15s in the back of a dsm without taking up the back seat space. Each sub should have about 3 to 3.5 cubic feet to run efficiently. Trying to mount them on angles in the hatch will be impossible if you want it to sound good. 4 12s might work as you can get them to work in pretty small box volumes. Have you considered smaller subs in a bandpass box? I think this type of box is more efficient. You get more bass from less space. These are difficult to build and design but I think it's worth it. I have only owned bandpasses because I think they are superior to sealed and ported. They are designed to play a certain band width, ie- 40 - 80 hz. I also build my own boxes after they have been designed on a computer program. I built one box with 2 12" Orions and it POUNDED HARD! That was for Paul Bishop in his 90 tsi. Also today's amplifiers are more efficient. That can also make a big difference when choosing to use smaller subs. Today, people are hitting crazy decible levels with only one or two subs. I had 8 12s in my Blazer. I only hit 149db. That's nothing nowadays. My problem was high current amplifiers but low battery voltage. The amps would pull about 200 ampres but my voltage would go down to 11 to 13 volts. They should see a constant 14 volts to operate properly. Anyways, just thought I'd give you something to consider. Most people think that because you have a lot of woofer surface area that there's is the sh!t; this is not always the case.

new rockford 15's only need like 1.5 cubic feet to rock....just some info...

I'm thinking about doing the same... I had a fwd, well, still have, its for sale, and I took out the backseats, built a fiberglass enclosure on the driver's side for one 12 with an amp rack that sat the amp against the back of the seat. Then to finish the rest of the backseat area I built an extension onto the factory console so it ran to the trunk area. Then built a little folding seat for the passenger side. Result: I had a 12" sub, more storage in the console, and 1 backseat along with a completely empty trunk area.

With the AWD I just bought I don't want much of a system, just something that's clean, clear and sounds good. I'm thinking a single 10 glassed into the back corner of the hatch with the amp against the vertical middle part of the back of the hatch so I can have my system, 4 seats and some trunk space.

I didn't actually make that one, that is a picture of a guys off of DSM Tuners... here are the final painted pictures of the one I made myself
http://www.ca.dsm.org/ubb/ultimatebb.php?ubb=get_topic;f=23;t=000129

That has "STEAL ME" written alllll over it.