Give it a try and see if it works. I doubt it will.
I’ve never seen any compelling measurements which demonstrate modal reduction below 100hz for any cardiod speaker. I can see it’s merit in reducing lateral boundary interference (100-300hz common sidewall interference range). But Kiiaudio and D&D have terrible floor bounce; one step forward, one step back. I bet the kiiaudio BXT module will eliminate the floor bounce. Maybe it can lower the bottom frequency for the cardiod response too.
I’m still waiting on some high resolution LF measurements which compare a normal full range speaker to cardiod speaker. There are tons of measurements, tests and mathematical simulations which demonstrate subwoofer efficacy. Subwoofers are way more effective (performance and cost).
There might be some misunderstanding here: the D&D's are NOT cardioid below 100 hz. The cardioid response stops at 100 hz. They have two "normal" omni subwoofers on the back, which fire backwards into the front wall. With boundary adjustment eq settings to optimize it. The idea is to avoid the Allison dip. Hence, the bass wave from below 100 hz will originate from the front wall, kind of.