I believe I used the new hole as a guide and dropped the drill bit into it.
Might have been 3/16th inch. The old one looked to be 1/16 inch.
Had it to do over again I might have used 1/8th inch and the flush valve barb might have worked better.
As an aside, the 3 flange gaskets were not used for my toilet for some reason. (Unless when they installed it the installer only used the straight wall gasket that goes into the floor drain. My toilet did not have the reverse (lip up) gasket installed at all.)
Lou, Laura, & Freya the wonder dog
2008 GMC Sierra 3000HD Crewcab SB Allison Duramax
2019 Flagstaff 8529FLS - Pullrite 3300
HAM CALLSIGN - KC3FFW