Thank you for those, always good to get more information.
The first one says it can be done to change male to female - but the resulting females' offspring are then all males.. I don't think I want those hens although the broiler raisers would. Its borderline and only 10% can be changed.
The funny thing is the second one says more girls with high heat for first 3 days and more boys with low (in bush turkeys). And it is because the other embryos die... confusion reigns!
Maybe you just have the magic touch - when you want all girls.. you magically turn them into all girls. When you want boys...