well it doesnt even have to be 1 inch... it has more to do with the shroud... the blades should be about half way out of it so it pulls the hot air out away from the radiator thus drawing cooler air in

:P well idk if thats the exact reason y... but i do know that it is suppose to be halfway out of the shroud... the 1 inch ur suggesting would have to fall under the tight engine compartment... and give room for the shaft that turns the fan to move in and out with out contacting the radiator...