Don't put any probes in the tub even if it is just for a thermometer, it is not nescessary.I set my probe on the middle shelf as well and I use no fan.Set your thermostat at 88 and start the countdown.I have had 100% hatch rate by doing this except I set my thermostat at 89.I have had clutches hatch anywhere from 53-62 days at this temp.Keep it simple,I see and read how alot of people complicate incubation of eggs.