i make this often for training purpose, actually i am training a center to an "guard" - and in the past i got some player who could play all 5 positions and are listed as C.
This SG stuff is just an purpose, and everybody should play and when the engine plays the SG as SF, and the SF as PF and the PF as C - maybe it was more logik but this wll definately crush your trainingsplans.