I did some measuring, and I actually do have 4 foot almost exactly between the wheel wheels if it would be possible to make it as shallow as possible(15").  I know I could build a simple box for them, and would be willing to try if I had to later but I am really just curious about the WO as I have never heard one before.  I can build it if we could figure out the design.  I have been installing professionally for almost 15 yrs and have access to everything I would need for the build.  I am just not familiar with this box and how to work out the demensions to get it to fit where I want it.  What I would like to do as I said is have it firing upwards through the rear deck.  I would like to build the box with the top/bottom out of plexe so that when the seat is folded down, or the trunk open you can see the box and what it is.  It would look pretty cool I think, can ya help?