Augsperger's cardioid looks very much like what Meyer is doing. A second driver 34" behind the first, inverted and delayed, produces the rear null. Within the cabinet, the rear driver might be assisting the front driver like a push-pull in spite of the delay.Would a U-shaped baffle with the leg length chosen for 1/4 wavelength also exhibit a cardioid pattern or at least a dipole pattern with reduced rear projection?
In any case, it looks like progressive cancellation at low frequencies is going to nix the use of open-baffle types for DJ use where weight and bulk are important considerations. I might try some in my sunroom where room modes are a problem and high SPL not necessary.
John