My measure of cow's individual performance is the ratio of her calf's 205 day adjusted weaning weight (AWW) to her weight at weaning.  My goal is to have every cow hit 50% or more.

It is much more likely a 1200 - 1300 lb cow will 205 day wean a 600 0r 650 lb + calf than an 1800 lb cow will wean a 900 lb + calf so this criteria also tends to show an advantage to having more but lighter cows per acre of pasture or ton of feed.

In cow/calf no matter how we market our product we end up getting paid by the pound.

In your case weaning at 120 days you would have to change the 50% goal. However a lot is going on inside a calf between 120 days and the standard 205 day weaning weight. I'm not sure the ww % system would work the same with early weaning. I actual like to go to 230-240 days and let Cattlemax correct back to 205 days.