You may need to switch to interior probe placement it is far far more accurate under erratic conditions. If you do so there are a handful of steps to insure safety however. I know Aaron tested flexwatt to only hit 100ºF but I have a strip that got far far hotter (old style) that would be the first replacement to something that will not get over 100ºF like ultratherm. The next is the probe must be firmly fixed (regardless of placement) and the third is I would use the hydrofarm as a fail safe in addition to the relay setting on the herpstat (if it has them) being enabled. It then will not matter at all if there is hot or cool parts (ultratherms in my experience are super even) and it will account for air temps and any other variations.