Where is the PSU located and does it have a bottom 120mm fan or a rear 80mm fan?
You basically want the PSU to be next to the exhaust fan, if you do that then they will not fight against each other.
As said, hot air rises but if your running a Phantom PSU in an Eclipse 62 with some decent fans, reversing them has no effect on the temperature, if the airflow is good enough it does not give the heat enough chance to rise to temperature sensative components.
Just need to basically have the cooling designed around the PSU placements, if its top rear then its front in rear out as usual, but if you mount the PSU at the front then you would have to have rear in front out etc.
Then if you mount the PSU at the bottom the best may be to.... you get the idea.
Airflow in a custom case is nothing like the standard cooling, the v1000+ has intakes only basically, front and rear so in and out is not the only way to do things.
If scientists have came up with that conclusion then please tell me how all of Lian Li's new cases work.