I would like to see how that operates with games under pressure from hawks. There have been times when greater size around 5 lbs is better than being 3 lbs. Then it comes to how size impacts survival against other threats.Natural selection will favor chickens that are closed to RJF in size, The larger breeds tend to get smaller and the bantams tend to get larger, all of the drifting to RJF in size in these type of scenarios
In my setting, the smaller RJF hybrids were taken preferentially over standard-sized half-sibling games.