I have seen no data either way. Some baseball geek from MIT should help us here. With low air density the ball would be subject to ambient conditions, I believe. With high air density, the ball may change it's trajectory with unpredictable results (it has more mas effecting it). That is my opinion. Based on my understanding of physics. I could be wrong! Wakefield 's arm slot/mechanics have to be consistent.This is not an "exact science". Go Sox!