Brian. I have 2 models on the go. 1 -uses twin MCM 606 drivers.Much better than you would think.Uses the ELF cabinet size,can go larger to get a lower FS. The next will be using the 879S and the 606 as the lower driver. Both will have treating to the cones.I went into more detail with Hank off the board. The treating of the cones is still in the works and has and does mean a lot of testing time. I am almost to the point of posting the final design.This will be more around the middle of next month. Uses a deeper cabinet that the ELF I have not fine tuned the cabinet as I am still coating the drivers and you know till the drivers are complete you can not go to a cabinet. But over all will be close to the ELF about 1-2" deeper at is it.