Just got the pieces fitted together for the Z stage for the first time. It moves! It lives! Surprisingly, the stepper motor driver worked right off the bat, unlike the two previous ones, both of which needed some fiddling. Probably the better soldering iron is to blame.
One bolt is about a millimeter too long, I figure I can dremel it down. Bigger problem is that one of the two inner pieces that hold the rail on is so short it can flip to the wrong side, plus the nail is loose. It will have to be redone, and I'm not sure I have a proper piece of acrylics for it. Also am missing two tube flanges. Once that is done, I am ready to mount the first tool!
My tool mounting is with some tie-down strap I got for DKK 20. I have 2x4 long holes they go through (nicely unsharpened with dremel and sandpaper) and they can be used narrowly or widely as befits the tool. It looks primitive, but I think it's good for flexibility and pretty damn solid.