I am not questioning your methods, because they do work (if you are culling the right birds., which I think you do to the best of your ability).All seriousness shubin culling is necessary to improve gamefowl as a whole. It sucks to do it and I will put it off until I have to. Inferior birds should be culled regardless not given away as cheap stags. I'd give my best away. They may be somebody else's mediocre birds who knows. If I am second guessing anything about them they won't leave here.
But this is what I think about hard culling... Of course some are better than others... Not everyone can be #1. But if you take that method too literal you would be obligated to breed only one best rooster to the best hen... Leading to a dead end in genetics.
Having multiple gamefowl of varying degrees is important in my mind.... For example... what the Kelso might lack, the Miner blues have, and/or vice versa.
Sure my Spanish dont stand a chance against my larger Americans, but that doesnt mean they are no good. They have other things my Americans dont, which when bred could provide some advantages...
As I mentioned I dont cull, but nature culls for me and pretty heavy. Not just predators, but natural fights, hens killing chicks, sickness, etc.. I tend to think some of these lacked something to a slight degree. some of it just bad luck.