If I'm in doubt for any reason about a carb level (such as steady hydrometer but under attenuated for what it should have been and refusing to budge), I do similar to raven. If it's real bad, I'll do the lot in plastic, if its just a nagging doubt, I'll do some in plastic and the rest in glass, and keep them warmer. With the PET squeeze test, though, I would chill the bottles first, and see how hard it is when cold. If in further doubt, I would open one early, at about 5 days in the bottle. If it is carbing normally, it should be undercarbed at this point. If the carbonation is correct, or is over carbed, after such a short period, then I make the decision the rest of the batch will need to be vented.
Never lost a single bottle, either pet of glass, to bombs, even though I had a few batches that were over carbed. I always managed to get to them in time.