Train him at PG position, the others are slower.
Between PG/SG and SG(80% of PG), I'm not sure, that's an interesting situation now. I haven't thought about that before. SG should be slightly faster, but PG/SG gives double more training slots.
I don't know exact numbers for two-position training, people used to say it's about 70% of the one-postition training.