Are the dual electric fans still running the full side shrouds? I think what PK is getting at is how can the air trapped by the shroud you made get out. I am sure that the answer is through the fan holes, but if the sides of the fans mount to the rad surface doesn't that in effect create a seal that would hinder air from moving from the aluminum shround area to the holes for the fan? If you plan on mounting the fans to the aluminum shroud instead of the radiator I can see this working, but I'm not sure if you leave the fans mounted to the radiator.