do you know what the CFM is on your fan? or at least what size mm it is or estimate size it is?
you want to keep the holes near the fan open, if you can stick your finger in them they are large
mine is small 60mm 19.2cfm my cooler has the plug open at the bottom thumb size and then very small holes three front top and three rear top (see image below) and then near the fan I have a 1/4" hole and same on the other side, so if your fan is much larger and pushing much more air you may close more holes, (just not close to the fan) and it sounds like your holes are very large
just dont mess with them too much after you get them set, never touch them later on during lockdown