His height will give you a slight advantage in training his guard type skills, i.e. passing, outside defense, etc. over training a taller player for the same skills. At the same time, it will give you a lower advantage when training his inside skills, over someone who is taller. He's not an ideal candidate at that height to train to be a dominating inside player, however, he will train to be a more well rounded player assuming that you put some focus on his outside game. Keep in mind though, where his current skill set is. For example, if he has atrocious outside defense, your going to have to invest a lot of time training him out of position to raise that defense level to anything respectable. This would hold true no matter if he has 6'8 or 7'8. However, he should train faster at the outside defense because of his height than if he was 7'8. I can not tell you for sure how big of a difference though. (Also, I'm just using the 7'8 as a randomly picked height, not sure that there are very many 7'8 players in the game. )