How to disassemble an HSC90?

TU81, it's quite a bit deeper. The side-walls appear to be just locked at the bottom and then hooked such that one can lift it up and off, like the TU81's side walls. However, they do not move no matter how hard I try. I don't find any screws holding them, though. And with the sidewalls on, I cannot remove the top-cover either. So, I was hoping I could at least take it into two pieces by moving the whole core out in one piece. Apparently that central unit is just screwed on the front, like a rack-mount device. Indeed I can move it out quite far. But then it stops at a protruding piece of the backplane circuit board! There seems to be no way to move that core all the way out other than by removing the backplane circuite board. And I'm not going to do that.