go big or go home
grill blocking is all based on how much heat your radiator needs to reject to the air. When I am P&G all over I have my grill blocked 100%. without P&G I needed about 30% of stock square inches.
Start by blocking off the top and seeing how engine temps do. If its fine then block off half of the lower grill. once the daily high temps go lower then ~50F you can block the whole thing off.
Grill block partial or full - EcoModder