Concerning 15sub dimensions, there are several reasons they are what they are. You brought this up on my forum and I answered there, over the course of several posts, mike. You were there to post so I assume you were also there to read since you quoted several of those posts.
The "matched depth" approach is inferior acoustically with the 15sub's intended purpose of working modularly with all the dedicated-mid-driver fEARfuls. As well as acoustic advantages to the current dimensions, those dimensions make the 15sub capable of matching width dimensions with any other fEARful model - the 12/6, the 12/6cube, the 15/6, the 15/6tube, the 1212/6, and the 1515/66 all work with the 15sub.
Even visually I consider the other approach inferior, with any one of these other fEARfuls. The new esthetic is that form follows function and the best is always more beautiful ; }
I won't be on TB that often, folks.