So now there is a luck factor in training?
Well, I suppose cross-training is random so it is technically luck.
I'll just say that I think the elastic effect can be highly underestimated. For the last two and a half seasons (since my 20 year olds were 18), I've been training JR on my primary team and 1v1 FW on my Utopia team nearly every single week. I'm trying to do some unusual builds with both teams, so I've been willing to accept the inefficiency that comes with that unusual training, but it's more extreme than I thought (or the training simulator spreadsheet has factored in).
I don't have an exact comparison to your player, but as an example on my side, I have a player who now has:
Age: 20, Height 6'6 / 198cm
JS: 11
JR: 4
OD: 7
HA: 14
DR: 16
PA: 6
IS: 8
ID: 7
RB: 7
SB: 7
With a level 4 trainer, his last driving pop was on 2/20; he has gone four weeks with 48+ minutes and still hasn't reached 17 in DR. The handling pops are generally coming every three weeks, still, since he started off significantly behind in HN vs. DR (which was one of the things I was looking for in my Utopia players).
I'll just add that the JR training with a level 6 guy is excruciatingly slow now.It is obvious that the game does not want to let you get players with extreme skills in certain areas without training other ones it wants as well. Luckily I don't care.
