Hole location for Herbie for overflow's

[Palmer]

It seems under the 42 " diamond saw it says its for 3/4" bulkheads. But from what I could see on the 1 " bulkhead it stated the hole size needed was 42 mm.... You just cant win sometimes... Guess I am stuck with 3/4 returns and herbie drains unless someone can think of something else I can do. You cant drill a bigger hole where the smaller one is can you? Not sure how practical that is and how to trap the water needed for the drilling...