I'm installing some foil-faced roxul board in my hearth near my insert. It will NOT be touching the insert, but WILL be touching the flex chimney liner about 1 foot above the insert (standard liner with the corrugated outside). I want to make sure whether my foil tape can attach well (temperature-rating-wise) to the 6" flex liner at that point. Approx how hot, max, does the liner get one foot up in standard use, in anyone's experience? My liner exits the back of the insert at about a 45-deg angle. The model is Vogelzang TR004, Btu 69K. I've got it all disconnected right now for the insulation work, so it's kind of cumbersome to fire it up and test it myself! Thanks for any ideas.