The simple solution is to cut threads in the hole you drilled. However, that might become a problem in the future, because someone wanting to lift
the mast might not realize that the screw holding the bail is also holding the mast. You deal with that my documenting it in your Equipment
You might also drill a very small "test well", say 9/64" diameter 2 1/2" above the deck. That will likely take you above the shoe on which the mast stands. If it doesn't, go to 3" above deck. Such a hole is too small to weaken your mast. If you have to abandon the "test well" and go elsewhere, just put some goop in it. "Bondo" or "White Lightnin'" body filler is good enuff to that purpose. When your find the right location for the hole, open up to the appropriate diameter for a tap to take your desired diameter s/s machine screw.
You can also use blind rivets if you would rather have mast and fastener made of the same material (ally).
Have fun :-)