Well considering that training is getting slower by the age, a good tactic to make him SF is start to work his outside skills, and then when those will be good enough u can switch to big men. Also u have to remember that training OD is training ID too. Wendon who if he is not the best SF of the game for sure is top5 is 6'10. Also considering that an SF needs more outside skills than inside, i think that u have in u r hands a great SF prospect. If you want to get the max of his potential, then u have to train 1 position.
Anyway his potential and his skills giving u the option to do everything u want