Swampdog
Claude says "hello"

Go into commissioner mode, pull up a particular you want to edit. Player page, lower left, scroll down to "peak start", and/or 'peak end". Change the age listed. The average age for peak start is 25, change it to 20, or maybe 21 if you want an earlier peak, etc. Same for peak end.

I like the suggestion. I forget about them at times too.

That's a good question. I've been thinking about it and I don't know either. I also don't know why you would want to adjust all players in the league in that manner, but each to his own. I would assume that if you adjust the peak start to +100, that would make the peak earlier, since that makes it greater, and the -100 makes it later, and lesser. Same for peak end. That's just a guess, though. I assume that you know you can edit specific players individually, and that would be the way...

You can edit fielding ratings, through league editor. Edit predicted stats. I do it for every team, every year.