I'm brewing on a herms system to help regulate mash temp stability and occasionally do a step mash and have been feeling that my beers aren't quite as light bodied as I'd like them to be for the mash temps I'm targeting (generally 147-149). I'm starting to wonder if I might be measuring the mash temp incorrectly and was hoping for some input. I've got three thermometers to watch my mash temps... one on the mash tun, one on the HLT, and one on the mash recirculation line just before the wort re-enters the mash tun. The HERMS coil seems to be quite efficient as the HLT temp and wort recirculation temps are always exactly the same. To keep my mash where I want it, I generally have to keep my HLT about 8-10 degrees hotter (I believe the proper term for this is delta T) than the temp reading I'm getting on the mash tun. What I'm starting to wonder is if I am correctly controlling my mash temp by monitoring the mash tun, or if I should be going off the wort recirculation temp? The fact that the delta T is 8-10 degrees would make quite a big difference in the body of the beer if I'm measuring at the wrong place. I get great efficiencies; my saisons and farmhouse beers are generally finishing around 1.001 to 1.003, so it doesn't seem like I'm doing it wrong, the dryness and body just aren't quite what I'm aiming for. Could be a water issue too, but thought I would see what opinions are out there from any experienced HERMS brewers. Thanks in advance for any feedback.