Grow Box Exhaust Location

Well I'm currently building my first grow box. Would I benefit on having say two exhaust locations, both on the left hand side but one in the middle and one near the top? I would use only one at a time. As I lower/raise the lights via the chains and S-hooks, would it be better to exhaust kinda across from the light or just at the higher point as heat obviously goes up...

Also, I was thinking to use a PSU from a computer and just jumper it to turn on and then hook up a couple fans, hang them on the right hand side, pointing towards the light. Better for those fans to kinda point towards the exhaust or not really?

And one more note, the exhaust pipe will be hooked up to the chimney for the water heater (which came conveniently prepared for me with a T-branch already installed!! woot!) which will have some vacuum, plus whatever fan I decide to place at the exhaust point.

Thoughts??

right at the top in the middle. and the intake right at the bottom.

At the highest point is where you want to go. As long as its up towards the top of the box heat will find its way there.

Ya I think you're both right... The more I think about it, the less I want to be moving exhaust locations around... Sooo &%*$ that...

Thanks for the input!!