Dont be so anxious about your u-21 players. The needless and mediocre ones just dont worth it. The good ones requires lot of Tokens to sign!!
I am at lvl 3 and my 5 star u-21 player (33/34/34) requires 21 Tokens to sign!!)
The most likely you will let them go. Building U-21 academy just dont worth it. It costs virtual money for nothing!! Trust me.
You get 5* players @ L3 are you sure, I must be in the wrong game.