Amazing job but the results are pretty different if I compare with my own jobs.
Anyway, mines are not as precises as yours. I may be wrong in much things, in others you should take a deeper look to your work.
I agree with you that most of the PF make his job better if they have a Center role.
I would give more strenght in your formula to the outside skills in the PF (much more), im sure about JS, but driving can be important.
And i also think that its not a 6-7 skill problem, i think that all the skills have an influence, sometimer more/sometimes less, but all the skills have their importance. That includes Game Shape and of course stamina. Free throws are not included. (or at least they are invaluable).
I would give also more importance to the RB in the SF...
You did a great work, it would be great if a BB comes here and gives us a little hint.
If we are astronomers, i just can say that BB is (by today) a very dark universe, everything is known in HT, and nothing is sure here. Maybe that's why I see BB so interesting.
Regards!