Hi Richard & all,
I wasn't there for my Coromandel MissyMoto->LittleMin->minim's first or second dismasting. I believe the eventual repair by NeedleSpar involved inner-sleeving the upper mast. I look forward to examining it myself, but I expect it'll give me confidence, maybe not for much open ocean sailing, but I think a sleeve is a decent solution. I won't like to see lots of rivets...
I was aboard for mehitabel's mainmast breaking-but-not-falling in mid-passage. That started at a 3/4" vent hole with a clamshell cover screw at either side, half a metre above deck, right in front of the pilothouse window. It progressed well into the substantial, otherwise adequate timber mast, before our eyes. Got somewhere, fixed it sort of, then in NZ unstepped, much reinforced and even shortened the mast in converting to junk rig, and all's well.
Best no holes! Especially forward or aft facing. But our guilty one is still partly there, heavily 'sleeved' and proven harmless.
Cheers, Kurt