I am debating which size air intake vent to get for my GH. It is about 500 sq ft and has a 20" exhaust fan. Due to it having one end dug into a hill, it only can have one vent opposite the fan end. It seems my choices are either a 24" or a 30" model (all fan/vent openings are squares).

I am leaning to the larger size, but would like to keep the vent as small as possible, but not too small, because it will go on the S side of the GH and block some sun (that hill again).

Just curious to get some experienced input. Do folks think the 24" is enough larger than the fan opening to supply sufficient intake air? Or should I go with the 30".

TIA