Wow never to old to learn. Thanks Ron!No, do not mess with the temps hoping to get more pullets. That is a type of magical thinking by those that do not understand the odds of head or tails.
Messing with the temperature is bad for both male and female embryos. It might be true that male embryos will die more then female embryos but the point is that both genders will die if you mess up temperature.
Pay attention: Chickens are opposite of humans. The female determines gender not the male. She is born with about 3000 embryos that are already male or female. The gender is set before the sperm fertilizes the egg. Nothing changes that. NOTHING!