Hi David,
Yes, that does work...I'd forgotten about that one. Unfortunately, in this situation it isn't quite what I'm looking for, as I have a few different shapes coded into the one object, and I only want the bounding hotspots for one of them: it's an irregular shape that can be rotated around its Y axis.
I guess I'd like to be able to access the info that ARCHICAD uses to calculate the bounding box. The only thing I can find is SYMB_A_SIZE and SYMB_B_SIZE...but they are only for listing and labels.