exhaust looks good, I would put up a barrier wall on the back of the s9's. don't seal it off but block the air so it can get sucked out by the exhaust fans. I would add cool air inlet fans on the opposite wall to allow more fresh air in. 4 s9's per 30 amp breaker with 220v, highly recommend a nice industrial power strip like a 30 amp knurr server strip. any more questions feel free to ask