My rule of thumb for 2-3 year old females is 1300 grams by the time I start pairing in October. If they're 1300 grams when I start pairing, they're pretty much guaranteed to hit 1600 by the time they ovulate. Even the 2 year olds.

Older females I'll pair a little smaller. I paired my 2007 female when she was 1150 grams or so. She still hit 1600 grams, and she gave me 5 eggs. But this last year when I paired her a second time she only gave me 4 eggs. I'm giving her a year off this season to gain some weight.

Making eggs takes a lot of energy and resources, and I think breeding small slows them down on their way to their full size. So waiting an extra year means more eggs in the long run, at least for me. My females are generally kinda small. (This is not a cue for husbandry suggestions, I'm just remarking that they're kind of small. They're healthy, and I'm happy with them. But I might start giving them a year off once in a while to grow.)