Just need to make sure to calculate the exhaust fan m3 air sucking capability and the hole for it, start with a small hole, if the intake air is only coming from the hole then is good, if the intake air is coming from the hole and other places then it means the hole needs to be bigger or make small holes only, need to watch out for thieves, holes larger than 20x20 is dangerous but if your place is very safe then I'd say larger holes are better.  A rule is, if you have a 50x50 exhaust fan then make a 50x50 hole but like I said before, it will depend on your exhaust fan sucking capability.