I guess about the only thing I can say is to start the fan up, and put your hand behind the intercooler and see how much air flows through. Then put your hand on the side and see how much comes out through the gap between the fan and the intercooler. If you can't feel it with your hand, try using a piece of paper or a match(making sure there is no flamables near by). You will most likely feel more air coming out of the gap than through the intercooler.
If you are going to mount it directly to the intercooler, I would try to mount it on the back to suck the air through, kind of like the cooling fan on your car for the radiator. If you can't get it mounted directlly on the intercooler, you may want to make a "funnel" type device to seal it against the intercooler. Good luck.

Tom