The idea of pushing air through a hood is simple physics.

When you pull the air through the hood the fan will work harder and still may not get up to speed. The backpressure of the motor working hard will also generate HEAT. Do you push air through the AC in your house or pull it through. You push the air across the coils not pull it across.

By having the blower outside and pushing air through the hoods the motor spins at full RPM's and has no back pressure to start with. Pushing the air will create a small amount of backpressure but with the motor spinning at full RPM there is no noticeable problems.

You can install it either way but my way the motor will last longer and produce less heat.

It's up to you.