venting an attic is a dumb thing to do in a humid place, sealed attics is the way to go.
it will cut your energy load especially if you install your air handler and duct work in the attic. There will be no solar heat radiating your air handler and ducts and there will be less infiltration in your home with a sealed attic.
That make up air should get connected right to the return air duct of the air handler. 4 inch may be too small.
I built a small 4 unit apartment building in the tropics, I sealed the attics, it works great.
make sure it is 'open cell' foam