Difference between 1.5" and 2" drain in overflow

[sphelps]

Originally Posted by christyf5

I'm of the understanding that in order to do a Herbie overflow you need two holes drilled. The overflow box doesn't have the space and the tank is already running so that ship has sailed.

You can do a herbie with a single large hole (2") but if you're having issues finding parts for a 2" standpipe then building a single drain herbie will be a much greater challenge. Here's a drawing for reference, if it's really something you want I could probably build it for you and ship it to you.