Lower grille block.. (question about ducted cooling path)

[Mira]

Hello ecomodders! Who knows what's got me up pondering aerodynamics at 4:30 am... But! I am planning to do a (partial) lower grille block, and have a ducted opening... I recall seeing in a thread that an opening 1/6th the radiator height will do, can someone verify/amend this?

And also, it should be alright to cover the area in front of the A/C compressor? I rarely ever use my A/C to begin with, but I need it to remain somewhat functional for defogging purposes.. Down the line I'll consider deleting the whole darned thing, but for now, it remains

In the picture attached: the blue area is the radiator, and the green, the A/C compressor.

[Gealii]

i stole the pic awhile back so not sure where it came from but i know this is the correct picture. for the opening to be 1/6 it is said the path from the opening to the radiator to the exit path must be completely sealed except at the entering and exiting air points