My nintendo cab is also 9/16. The white nintendo tmold from t-molding.com actually didn't fully cover the slot, I actually had to paint on both sides to the tmold slot so you wouldn't see any white from the primer. So, I can only assume that it is slightly less than 9/16. So if you go with 3/4, get some 3/4 inch tmold or else you will have teeny-tiny tmold on big daddy mdf/plywood/etc.