ORIGINAL: Argess
I always measure mine at the glowplug.....point the temp-gun down the cyl-head hole. The glow-plug temp is pretty constant summer or winter (with the same tune), but the fin temp can really drop on a cold day, or climb on a hot day, so it's not consistent with identical tunes.
I find it odd you got higher temps at the fins than the glow-plug. I normally would get the reverse of your readings.
From the way he described it, sounds like he was reading the temp on the crankcase and not the top of the head.