Hi there! Not sure there's much to be said. He will train in big men skills slower than if he was 7'4 and he will train in guard skills slower than if he was 5'10, but I don't think this slowing down is quantified. 6'7 is a good height for an SF, I think. You'll need to give him training in big man and guard skills, so it's probably better to fit him together with other more specialized trainees. Something that might interest you is that JS and JR train at the same speed regardless of height (I've seen this before in a few threads, not 100% sure)