One of these days I'll figure out how to balance the online and offline worlds but for now it's just good to be talking at you again :)
Methinks you give me too much credit and yourself not enough. Shooting with a lightbox or in a studio has never been my thing, I just sort of fiddle around it much like you. Let me know how it goes when you build you one, I built my lightbox, a cardboard and cheesecloth affair, and I've never been able to tell if I'm doing something wrong shooting or if there's something wrong with the lightbox build. So mostly I just fuck around with in once in a while in that fumbling, stumbling, knob-twiddling manner.
I was thinking of making it from coreflute and using the pattern of the one I have as a template - it opens up flat then folds together. That way I just need to double up the measurements and I'm left with one twice the size. That's the plan anyway. It won't be foldable as I'll glue/tape it together for structural integrity, but it will allow me to get larger items in there so I can fumble, bumble and knob-twiddle on a larger scale.