Difference between 1.5" and 2" drain in overflow

[Reefer Rob]

What an ingenious little bit of plumbing! I have 2 holes in each overflow, so I don't need it personally, but I think a link to that should almost be a sticky somewhere.

One thing I was thinking. What about eliminating the 2" standpipe inside the overflow. This should increase the flow potential and reduce detritus buildup in the overflow... just a thought.