If you use the “centre point of piston travel” method (as in Technicalities) you can find the exact point of TDC, then 2.4″ on the flywheel periphery to give the optimum max advance figure you can’t go wrong.
And (as the author of said technicalities article says) if you mark the flywheel at that point, it’s makes roadside checking/resetting so much easier.
