Quote: 36-38% RH is the range I maintain in my Dickey cabinet (then for lock-down they go into my GQF cabinet hatcher with around 78-80% RH).
My experience with hatching large eggs like Pea and Turkey eggs (that are laid by my own Hens here, in my very dry climate) is that with the incubation RH being any higher my chicks and poults grew too big inside the egg and had a harder time hatching... they seemed to get themselves malpositioned, pipped at the wrong end, or quit during lockdown more often. (The lower RH also works well for my Quail, Guinea and Silkie/Showgirl eggs).