Quote (Subwoofer @ Mar 25 2017 04:33pm)
http://www.rockfordfosgate.com/rftech/box_wizard.aspwill give us a general idea of how much air space you have to work with.
the next step is finding out which side of the box will be best to mount the subwoofer on given the subwoofers depth and mounting diameter.
from your pics it seems there are some angled surfaces that will interfere with it sitting perfectly flat. the easiest way to figure out the rest of your box is to have the bottom board in there to give you a flat surface to measure off of.
once you know what the bottom board measurements are you can simply measure how tall it can be from that point and you'll have the specs for a basic rectangle box.
after you have the box specs worked out you'll need to find out the air space and top mount depth(how deep it is for the subwoofer) and we can start looking at subwoofer options.
as for the red areas i'd probably just build amplifier mounting spots in that area. mounting them on the subwoofer box itself has a number of drawbacks which are best to avoid.
rear speakers are completely up to you but imo you can forgo them for now for simplicity sake and simply see if a set of amplifier components is enough before worrying about adding more.
now for that middle sloped area i'd just leave it alone for now and focus on a simplier square/rectangle box design rather than trying to build a T shaped box.
that turned into a text wall quick lols
Hahaha
I like wall of texts, it's my nickname
lol
Anyway, when you say which side to mount the sub on, are you talking forward facing or skyward facing? (Just trying to follow along with what youre explaining).
If so, I think the best option would be skyward facing, right? More space to play with for a larger sub + We could make the box completely rectangular (I'd add a shelf to that area behind the seats that a large box could sit on as well if we wanted to house a 15sub or something like that) and the amp mounts could go on the side/bottom there.
Is that kind of what you were saying? (Trying to make sure I'm following your train of thought here).
Doing it that way would also make wiring pretty easy, which is nice
edit: Will forego rear speakers for now, I think that's a good plan
What sort of wood thickness should I use on this calculator?Would it be better to have 1 large sub (rectangular enclosure, skyward facing) or 2 medium size subs (wedge enclosure, angled up/forward)? Both would be viable in the space I have 
I'm going to go take some cardboard down with me to the car and sort of draw/cutout the amount of space I have, demension it all, then we can play with this calculator to see what we can build
brb
This post was edited by Textbook on Mar 25 2017 03:55pm