Electric - Pusher Fan ?

Before you do anything else make sure that you've sealed all any and all areas between the radiator support and the hood. At low speeds the engine heat can go over the radiator support and through any holes in the support and get recycled through the radiator. This alone can cause your temps to be higher, that's why the factory installed a radiator support to hood seal on most cars. The seal also helps to funnel air into the radiator on the highway as opposed to the air flowing over the radiator. The seal also also keeps the engine heat in the engine compartment.
But to answer your original question: the pusher fan won't interfere much at all, plus you could leave it on all the time??
Treblig