I used a 16" perma cool fan that pulled 2950 cfm. I did not use a shroud and that fan kept the temperature at the level I liked. The way I look at and some testing on a circle track G body when the car is moving the shroud can block air that would travel through the radiator cooling the fluid down. If you have a mechaincal fan and a shroud that funnels the air to the fan that helps, with an eletric fan that is mounted directly to the rad a flat shroud would hinder the air flow. Currently I have a Perma Cool 16" standard fan that pulls 2350 and the Perma Cool high performance 2950 cfm fan pushing as the back up. I have removed part of the front bumper to remove some weight and to give it a different look which allows the air to travel directly to the rad