I agree. People are afraid to strike out on their own and try new things because of the scare of "absolute certainties" that will happen that in fact are not certainties. I disagree with many things that the "experts" tout as fact and until my hatches prove otherwise, I will argue against them.Interesting. My best ever hatch was the last one. I set 25 eggs. 23 went to lock down. Hatched 22. These eggs were incubated horizontally until lock down, and I then put them upright in egg cartons. The horizontal decision was a "just because" decision, b/c I wasn't pleased with the stats of last hatch. The egg carton, upright lock down was b/c the eggs hadn't lost enough mass due to frequent rainy days which kept my humidity up, thus air cells were smaller than I wanted to see. These studies go to show that the "we do it this way because that's just the way it's done" mentality is worth challenging. I also hatch in a forced air at 100 degrees. IMO that extra 1/2 degree makes all the difference in the world with my hatches. I typically get one or two hatches late day 20, most on day 21, with a lot of break out right around the "hour of set" and a few late bloomers which are often dry, sticky, or malpositioned on day 23. I assist those as needed with a "hot tub hatch", and typically can't tell which ones they were 24 hours later.
Perhaps I should do a set next spring at 99.5 and see if that changes my percentages. However, if you are able to bring a high percentage of your lock down eggs to hatch, and still end up with a high percentage of females by doing egg shape selection, the temp shouldn't matter b/c you won't be loosing those males to temp issues. Also, IMO, certain hens are more apt to produce female offspring. Time for a study to select those females, and then do a study specifically on their eggs to: compare their shape to the shape of the eggs of their flock mates (specifically to the shape of eggs of a female who more often produces male offspring) Then, take the former female, and do an egg shape study based only on her eggs. Do the same with the latter female. Then, it may be time to work on culling the latter hens from the flock, if they can be identified.
I too was wondering if hens (since they determine sex) are more inclined to lay a majority of one sex thus providing the fact that (if there is anything to egg shape and sex) shape of egg is consistant to the hen. It'd be interesting to see if hen A lays predominately rounder eggs and you take 6 of those eggs and hatch them out along with 6 from hen B who lays more pointed eggs, will hen A's eggs produce girls while hen B's eggs produce boys?? If so then it would be a breakthrough to laying eggs from a hen that produces majority of pullets.