Quote Originally Posted by George Nova Scotia View Post
With a Type K probe near or touching the metal frame the temp rose to over 350F within a minute (focus). It would seem that we are operating at or over the spec for glass.
I don't think so. Schott reports about 350 degrees Celsius, which is 662 degrees Fahrenheit, as the maximum allowable operating temperature for their tempered hard lined interference glass. If the same value is true for the tempered HA glass, than 350F (178C) is well below the maximum value.

I haven't had issues with the HA glass breaking, even when running the head multiple times in FOCUS mode close one after another for extended periods of time (minutes).

Remember also the bulbs and glass is force cooled through the fan and accompanying small ducts ending above the lamps, precisely to protect the bulbs and filters.