I do not believe you can run the fan in reverse like that (some preliminary googling says no). I believe you have to flip the motor over to run it in reverse.
Do you know that it blows outwards? That would surprise me, it seems to me the efficient way of running the fan on the Rapid heatsink is intake down so that it spreads out across the heatsink evenly. If it blows outwards, that seems pretty inefficient to me, but I'm no pro, I just think that positive pressure removes more heat than negative pressure across a diffusion material.
Does anyone reading have this heatsink/fan and can confirm? From some googling, it looks like with PC fans, the hub side is usually the intake side, so in the case of this fan, it looks like it's already going to blow down, though I'm sure they can be modified when made, so not 100% till someone confirms.