My two F3 boys have the same parents, just different litters. I am constantly comparing them to find the subtle differences. It's a genetic crapshot, and I should know better. It's like trying to compare my two sons. Even with the same parents they will be different and unique. John Popp is dabbling in size and weight issues over the generations. He might be able to give you a reasonable range.
But it just doesn't matter. The personalities are huge. so...... thinking about number 2 yet?
John impresses me as a smart dude. When he gets all his data assembled, and the bell curves are graphed for all generations' height at front, height at rear, length and weight, then I'm sure he knows that the only thing meaningful will be the MEANS for each parameter as well as the AVERAGES. That is, of course after spurious data like the highest 5% and lowest 5% are discarded.
Do I think about another SV? Yes. There are 2 things that discourage me:
1: A mate for Louie will steal him from me and I'd no longer have his full attention.
2. Since I've finally reached a comfortable spot with him, after dismantling 1/2 of my house and furnishings, I'm not too keen on starting all over again.
If I ever see any signs of unhappiness in him, then I'd seriously consider getting another. I'd use the same cattery, and next time would go there in person to make my selection. It would, without a doubt be another F1. Louie is as loyal and energetic as Jessie, my black Lab was.