Overproofing

This past weekend I made up some BBA Ciabatta.  I'm dealing with trying to learn to time my brick oven being ready and the bread being ready at the same time.  I learned 750 is too hot and about 600 hearth and dome is about right for Ciabatta.  Anyhow, I got pretty good ovenspring but I didn't get holes to develop like I want.  It's not what I would call a Ciabatta crumb but had hints of good hole development.  During the bulk ferment I folded twice but have a feeling I was a bit late on this, ie the bread had fermented a bit too long.  What's a good way to tell when bread (in general or specifically Ciabatta) is ready to be folded or when it is ready to bake?  I can tell on certain types of bread but have a hard time telling with Ciabatta, especially when it's ready to bake.  Anyhow, any tips or thoughts you guys have from experience is appreciated.

Ed