There are lots of wives tales about things like that. If any of it were proven then hatcheries would be making sure they didn't hatch out roos. You are more than welcome to run your bator under the recommended temps for still air, I'm just letting you know what the temps are recommended to be. I hatch in a still air and I need 99.5 (anything less than that for any prolonged time is going to cause developemental and hatch delays. My next to the last hatch hatched out 7 out of 12 roos. My very first hatch I had a bum thermometer and when I thought it was 99-100 it was 93-94F the ONLY survivor of that hatch was a boy-not a girl. The female's egg determines the sex, it's as easy as that.
