The reason for the simple build is there isn't much room in there, and the main driver mount provides a solid bracing in the first place with double-thickness. It weighs a lot though too. Spikes or rubber feet are advised to keep it from shaking and moving across the floor. It was 3 trials to get the right combo of output, size, extension, and alignment. As another put it- this design is a bit of a unicorn.
As to knowing what I'm talking about, I'm likely the biggest speaker dork you've never heard of. I've been building since about 1999, and strongly since about 2007. Over 50 designs under my belt to boot. Others in the hobby are surprised I don't do it professionally. Meniscus actually sells 3 or 4 of my designs as kits as well.
Wow- I've never known Mad to be that cruel. To have errors though, I have known of that. At least you were able to resolve the problem.
Side note- I actually designed a speaker with the same drivers as the ZD5 in a different cabinet around the same time as Krutke did his. I didn't even know he was working on one. We both achieved a great result through separate trails.