Hey HeroCrank. first off, thanks for the threads, they make great reading material. I have to ask though how confident are you about the actual temperatures that you are pulling off that camera?
We use a Flir at work as well and when I talked on the phone with them regarding calibration they said it isn't necessary because their camera is not meant for accurate temperature measurement only differential measurements of instantaneous conditions.
When I compared the temp readings against a Fluke IR thermometer and a Honeywell thermostat the Flir was reading about 4-5 degrees above the actual conditions.
That said the delta T should be accurate in your calculations which is the most valuable data. Have you taken multiple captures of the same area over the course of, say, 10 seconds to see if the values are repeatable?
Sorry for nerding out on you there...