Alas, I don't check in often, but I'm still building speakers, mostly other designs. Not to downplay BFM but customers tend to follow the crowd of whatever is new.
Concerning the 1.4" CD, I don't make it fit. It's on top of the DR with a larger horn and lower xover. Obviously doesn't work with multiple cabinets in a line array but it works very well with one cab per side. A lower xover point with a quality CD driver and bigger horn helps with pattern control and phasing. It just sounds cleaner to my ears.
Now I do like the sound of the wood horns. They build easily in 1/4" ply. Just use hot glue and PL to assemble. I'm curious what the cutoff frequency is for those but I'm too lazy to figure it out. I also haven't checked clearances in the DR 250 or 280. Maybe 1.4" drivers would fit with neodymium magnets. And modifying the throats.
My thought is a DR280 with a big horn on top would sound lovely at potent volume. Haven't built a 280 in a while though. I bet it would be nice in 1/4" or 3/8" ply.
As you may discern I'm not afraid of having a little wooden resonance in my horn speakers. Every material has a sound. Kevlar, carbon fiber, poly, paper drivers all have a sound. Sure, in live sound after you get past the sound check they all blend together. But in critical listening the warmth of wood is nice.
Construction with 1/4" is straightforward. I use 3 braces for the outer walls. The inside throat horn assembly lines up on the line. Build the throat horn assembly to the inside lines. Build the rest of the cab to the outside lines. I also build the inside part of the DR as one assembly. In other words I make a curved top and bottom and once assembled build the outer box around it. Easy to do and makes everything fit well.
Oh, I also use concrete form tubes for the back sheaths. Strong, easy to cut and fit.
For unmatched sensitivity.