1/2 inch on the bottom is still a rather large opening for 240 ish temps. I've seen folks have it down to 1/8 inch or so on the lower vent and the daisy wheel hardly open. I cooked on the pictured egg for months before changing the gasket. It's always easier to come up to temp than down to temp....
If you want to find leaks, get the egg smoking strong and close the upper vent and open the lower vent.
