This might be a silly question... I use a square cooler as my MLT (photo below, ignore the piss logo, it came on the cooler many years ago) so my grain bed is usually fairly deep. I'm in the middle of a mash right now, and I'm curious how deep into the mash should I be measuring the temp? I have a standard thermometer standing in the corner so the bulb is at the very deepest point, and it's reading 156... however when I bring the bulb up to where it's only a couple inches into the mash, it drops down to about 153. My target was 154, so I'm probably a bit high I'm assuming?