I understand restriction but any restriction is there whether the housing and support structure is on the front or back of the radiator. Open a window in your house then put a board over it. It makes no difference whether the board is on the inside or outside, the air is restricted the same.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.