I wouldn't leave your main trainee's minutes until the scrimmage. If he fouls out or gets taken out for a random GE substitution, he won't get 48+ minutes for the full training.
Either pick a winnable league game even with your C at PG or just play him at PG in a league game you are going to lose anyway. Might as well get something out of that game (training minutes).
And in V you can play a big man in the PG position no problem, probably even without having to do defensive switches though that is probably still a good habit to practice for later.