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.