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 and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW