After about a year, I finally got some decent drivers in my WO for 15's.  I used a pair of 15" madison Knights.  The sound is very large, very deep and very powerful.  So far I haven't a chance to put it in by Blazer.  I'm using it in my home theater right now and it's pounding the heck out of my house.  I think my wife has had about enough. I used the cone area of 10's and simply scaled up the internal volume of the entire box to match the cone area of the 15's.  I did it that way so that it would still fit into the back of my Blazer.  Dimensions came out to 30x36x19.5 tall.  The biggest problem was the extreme angle of the baffles.  They must be made to be removable in order to mount the drivers.  Also, due to the extreme angle I had to cut some relief into the sides of the box in order to clear the driver flanges.  Here's the pics

sweet now get it into the blazer and come visit me.