Why building a Tympani??
I would go for a "DMW XXL" which would really extend the smaller(and even the bigger) models and give them more slam and punch.
I think with 3.7, 20.7 and Tympani they would eat their own money, because they would have to many models.
The benefit of the Tympani was not just the second bass panel, but the separation of the bass from the tweeter and midrange, which lowered IMD in the more sensitive freq range. This separation also allowed a split cofiguration that allowed you to place the bass panels for best bass and the mid-tweeter for best tonal and imaging performance. With today's DEQX etc, it is even more useful to have this separation since you can retain time alignment.
I would guess that the way to go would be a 20.7 mid and tweeter section, a higher tuned 20.7 bass panel, and a lower tuned 20.7 bass panel. The result will probably be close to 500 lb and cost around 30k if sufficient numbers can sell. Alternately, it can be a custom product only made to order on a cost plus basis.
