You'd need hundreds for a viable 'test'....but you know that.
I have hatched several small batches of 'torpedo eggs'. Approx. 50/50 ratio male/female.
Yep, not only hundreds of eggs but also many many different hatches to take into account any variables there to get a statistically relevant sample. Hatches by different broodies and hatches by different incubator, take out all the variables you can. Sounds like you've had fun playing with it too.
That's for sure!