Just a few thoughts-
WYSL- It is an age based tournament, if you don't like it, don't play.
There is a cutoff date, does it make sense that it has to be Aug 30/Sept 1? No, not really, but they have to have some date and that's what it is. Don't like it, don't play.
If you have player born before that cutoff date, guess what, they are too old. Don't make excuses, it is what it is. "Well Johnny is a '26, but he was born 3 months too early." Guess what, he is too old, sorry! Or maybe play for the U14 team. I hear about the 27's playing up for the missing overage 26's. Why cant your 26 play up for the clubs missing overage 25's?

Holding a kid back to be the "king" of middle school lacrosse? Guess what, only going to hurt him in the long run. Size, strength and speed will equal out over time, naturally. Seen too many kids get by on their physical advantage, only to fade away as they go from MS to HS and HS to college.