I almost forgot to remind you, be sure to seal the wood core in the holes
with some epoxy to prevent dry rot.
The best way is to build a 1/8" barrier (a quick way to do it is to drill a
1/2" hole, fill with thickened epoxy, let it cure, then redrill to 1/4" - or
whatever sized fasteners you're using).
Even simply coating a 1/4" hole (that you worked the drill around in to
enlarge it a teensy bit) with plain, unthickened epoxy is *much* better than
leaving the wood unprotected. Just use a Q-tip to apply the epoxy inside the
hole.
Then use the polysulfide caulking for a final sealant.
Best,
Judy