I am satisfied with this arrangement and probe location for now.
With these buckets I can't get all three at the same level. But after the fermentation kicked off overnight and the fridge is running less they have all equalized to the same temp. (Theremowell reading is 62F, all buckets read 66F with an Infrared Theremometer) Is that really how much temperature gradient there is in a bucket? Or am I getting a bad reading?
I think the initial temp difference was caused by cold air falling to the bottom of the fridge. The fridge ran constantly at first since I was only able to chill to 81F (with my Blichmann Therminator Plate Chiller). It was a warm day and my water temp was 68F when I started brewing at 6am... probably warmer when I was chilling at 10:30am.