The temp stays in that range because that is where the thermostat is set to open. You are getting plenty of cooling air -- and it is possible that more air is passing through the radiator with the block: on some cars, air comes *out* of the upper grill.
As long as the temps are okay, you can try blocking some of the lower grill, too? Are there ways for the air to "escape" out through the chin area?
My grill blocks are year round, though I can pull them out on the hottest days.
I'm down to a 15" x 4" opening, and all the holes in the chin panel are blocked, so the air that does go through the opening, passes through the radiator.
http://ecomodder.com/forum/showthrea...tml#post209920