I used this exact method 1 1/2 years ago with great success. I did it just for fun and before I set my eggs, I used the pendulum. If it showed boy, scrambled eggs, if it showed girl, it went into the bator, if it showed nothing, it wasnt fertile, scrambled eggs again. I ended up setting one egg that would be a boy and one egg that the pendulum could not decide boy or girl. In the end, out of about 12 eggs, I got 2 boys. The one I know I set and the one that was undecided. All the rest were girls. Maybe I got lucky, maybe it worked, who knows.