Elizabeth Hoag -
Through my work at the Corps of Engineers, I know that sometimes such work
is monitored on the structure at risk with electronic vibration monitors,
and that there are engineers who specialize in this kind of work.
Admittedly, this is usually to address issues of liability, and learning
after breakage that the construction really was at fault is not much comfort
in the case of the loss as something as unique as stained glass. I'll ask
around to see if I can get some names, because these companies surely have
additional expertise in evaluating risk before the fact.

If you are the Elizabeth Hoag that I think you are, we miss you in Richmond.
Tim Thompson