I'm incubating them in the RCom20 Pro , and yes , it does reduce from 37.5 to 37 for the last three days , I successfully hatched four ducks in the pro , but after my disaster with the dewlap toulouse(now known to be difficult) I decided to try and cover all bases by doing the last three days in the still air hatchmaker with the humidity factor helping with the sticky shell problem , 38.5 seems about right to me.