I recently purchased a new mast base from Steve Seal. My mental notes from discussion with him follow. Use at your own risk.

Ideally 2 large sheet metal screws should be used, one forward and one aft in the base. Through-bolting is not necessary. While you're at it, relocate the base 1" aft of the factory position, which is class legal maximum. Chainplates will be 1" forward of the center of the base (I think I'm recalling that correctly--I haven't installed yet). The usual boat wrenching rules apply: overdrill/epoxy fill/re-drill any holes in the deck, and use plenty of sealant--especially between a stainless base plate and aluminum mast base. As mentioned somewhere on the mailing list, the boom and mast base plate (assuming you use one) apply torque on the mast and base, but nothing a couple of well-mounted and appropriately sized screws can't handle. Lateral forces from the rig aren't a worrisome factor. Compressive forces, on the other hand....