[IsaacCarlson]

It would be easy to build one and I don't think it absolutely has to have rounded sides. The rounded sides just help the air expand more smoothly and help the air build pressure so it doesn't just blow through one spot on rad. If I can get a hold of some coroplast, I will try it. I know it will help a lot in my case because most of the air goes around the radiator anyway. I did manage to get some small-holed hardware cloth over my grille opening to keep rocks and bugs out. They were doing a number on my radiator after my condenser removal.