Hey Don,
You may recall I do have the FASS, and so far all is good

!
I do not have an answer on temperature. And, it will be end of June before we head out again. When we do, I'll get some infrared temp readings once we've been on the road for a few hours.
If no one else with the FASS on a CC has info, you might want to move this to the Cummins section, as SOB owner's also have FASS.
And, give FASS a call and ask them for input on 'How hot is too hot?'. (Warm to the touch? Hot, but not so hot that you can't keep your hand on it? Hot, and so hot that you can't keep your hand on it? Etc.)
Will follow this thread

! Even if it moves.
Best to you,
Smitty