Ok I will flip it. Because isn't the heat going to rise to the rest of the chipsets then? IDK. And what if a bolt falls in the hole where the fan is? Hopefully not. Thanks.
The fan will expel the hot air faster than it can rise. Seriously.. if the MFG designed a PSU with this flaw it would never have made it into the market.
As for the loose bolt, I'd be worried if there IS a loose bolt running around in your case, as it would far more likely hit a component and short it out. Just be sure that when you are replacing a component, you put your case on its side before you begin. Keeping it upright can lead to you dropping a screw into the PSU, making it VERY hard to recover (I've done that twice).