I've got a UAII, so I'll weigh in. Granted, mine was purchased as the kit, not built from the plans.
The back doors are screwed in from the rear, which means you have to unscrew them to get at the guts. My 3-Koam Z-Back is the same way (Real Cabinet!). They are not secured from the sides.
The cabinet splits in two via internal camlocks if you want it to. It's very sturdy, however. I've beaten the crap out of mine.
The design is definitely not like any "Real" cabinet out there, but I love it. It plays well.