I'm a bit reluctant to do a build thread because I don't know what information is copyrighted, but I'll post the finished product. I'm building one at a time due to cost and availability of workspace. Most of the modifications I am doing are using a B&C woofer (TS parameters within specs of the design of the cab, but has lower frequency response that I value as a 5/6 stringer), using an Eminence APT 200 tweeter on a 90 x 90 biracial horn (mainly because I already had a pair laying around), added extra bracing inside the cabinet (stiffness is better for driver performance and loss of internal volume can be made up for by acoustic stuffing), and using a stronger glue for all joints then sealing as opposed to an expanding polyurethane adhesive (literally the weakest adhesive for woodworking, I've used the glue I have to repair a broken headstock so I know it is STRONG).
I may buy pre-assembled crossovers due to a few of the parts I need to make the ones in his design being out of stock. I won't call adding an L pad a modification as it's an optional accessory included in the original plans.
The BFM forum is not very helpful: I recall asking for a suggestion for an 8 ohm 3 way cabinet and got tons of suggestions for 2 way cabs and criticism for only wanting a specific impedance (which I need to keep all my gear compatible with each other) and accusations about not knowing how to impedance match (I've been impedance matching for 20 years). Everyone on the forum acts like the plans are Holy Writ then you buy a set of plans and they state repeatedly that the dimensions aren't super critical, as long as you can stay reasonably close. It even says to mount the tweeter wherever it fits, but for best results, as high up on the front baffle as "practical." That forum almost drove me away, if it hadn't been for actual response curves where I could gather the data I needed without having to talk to anybody, I wouldn't have bothered. D.B. Keele and John Inlow can both do the same thing Bill can, although they may differ slightly in execution. Having bought John's plans for his folded horn sub, I would easily put it against a Tuba 48. I would even put a vertically stacked pair of John's compression driven 100Hz mid horns on the same level as a Meyer MSL-3 if you matched a high quality CD tweeter to it.