I usually train them at SG.
Train PG and SG:
Game 1: Place PF in SG position, then change the defend assignment accordingly.
Game 2: Place C in SG position, then change the defend assignment accordingly.
So far, there is no adverse impact at all.
PS: I tried to place PF or C into PG position (one position training), and this would affect the game (many TO and zero pass).