I have never kept track of the combination of factors that results in any given orifice size curing the overlap. I just keep putting in smaller sizes until it just starts to flair, then I usually go back .005"-.010" larger.

It helps to have access to the numbered drill bits because the fractional ones are usually too large of a step between. Although a 3/32" (.094) might be a good place to start.

The .075"-.100" orifice was just a suggested starting range so as to help minimize the number of times you might have to pull the pan.

Dorman 3/8" cup expansion plugs part #555-115 is what I use.

Trial and error is the only way I know to get it right on any particular combo.