If you have a 7'1" PG, train him in C skills. He will train very quickly because of his age and height. Then you will have a C who can handle the ball and pass and still do the inside work. He will be a better all-around player. Same with the 6'4 C. Train him in SF skills- he already has the inside skills.
Granted, my team is in a league with only a few owners. But, my four best players can play any position and play it well. I have played two seasons now and my combined record is 39-5 and a two-time Champion. So, maybe having a huge guy with PG skills isn't a bad thing, if you develop his bigman skills.
Once I scored a basket that still makes me laugh.