On the one hand, I know for a fact that that "10% of your brain" statistic is nonsense. Humans do use their entire brain, just not all of it at once; if your entire brain is receiving signals simultaneously, you're having a [i]grand mal[/i] seizure. On the other hand, it's very nearly the sort of BS pseudo-science that Araki occasionally likes to toss into his stories, e.g. "zero gravity means you pee yourself because your kidneys think you have too much blood".

And then again, the very nature of Stands as psychic powers renders the point moot either way. My opinion is, go with the ability to balance on anything, perhaps expand it to encompass the more general ability to balance things aside from just the user. That could lead to some fun and improbable physical phenomena.