You’re welcome Cat. I’m not really a fan of that entrance reducer. It’s fine for a small colony while it’s building, but doesn’t allow for a gradual buildup of a colony. A respected American beekeeper (Tom Seeley) has done a lot of research and settled I believe on 15 sq.cm. as the ideal size entrance for a strong colony. With that in mind, you can allow 15 sq.cm for a strong colony, starting small and gradually build up as the colony grows. In inches: that’s 3/8ths of an inch by 6 inches.
You can improve the entrance by allowing 2 small entrances, one on each side. The purpose of that strategy is to allow the bees to draw air in on one side & expel it on the other. That’s the way I set my entrances up when making new bottom boards.
In relation to summer heat: Keep the entrance relative to the size of the colony, and no more, with no added ventilation. The bees will air con the hive via the entrance. Added ventilation will only work against them.