Sounds kind of big, Better start at 1/4 and reconnoiter. Not like there is a flood in there. Part of the reason they are half moon shaped, with the flat against the inside, is to minimize visibility with good drain effeciency. Tucked inward. So you may not like the 1/2" diameter look. Be careful.
If worried about drain efficiency, add some extra 1/4" . Tuck the 1/4" holes right near inner wall like they did.
I am suggesting this never having an AD and don't have one to look at except pics. So please just consider my comments as brain storming.
If the half moons are 1/2 (Diameter), it would take 8 x 1/4" holes to equal (ouch!)
