After my new trainee finishes with U21, I will fire my trainer and dedicate half a season to ST and FT. In the meantime, I'll buy 5-10 18y olds, Perennial allstars/Superstars for cheap and hope they will get some pops, then sell them. To me, that's the only feasible way to get something out of crosstraining. Using CT to actually train players and then expect them to play an important role in your team - I think it's not.