Ah....the RAIN question.
We had a lot of that at Carlisle this year (ask Lane) and we found that those cars that did not have drain holes at the bottom of the air channels under the engine cover soon filled the channels with water and, when it began to trickle out, it lands right on the air cleaners. Then, when it becomes hard to start, the owner opens the engine cover to see what's what and dumps about another quart of water onto each air cleaner, thereby saturating it. Put those two together and we had several waterlogged cars and at least one with hydrolock (the water ran into the carb, down into the cylinder, filling it, and preventing the piston from going to the top of the cylinder).
Not a good time. Opening up LOTS of space under the grill (as Alan has done) is fine, but he and a bunch of us now make sure the drain holes are in the channels over at the sides of the cover - take a look at the cover underside and you'll probably see where they should be.
3/16" - 1/4" should do nicely. Let me know if you need a picture and I'll take one for you
The other thing I would do if I lived in Hawaii or some other mega-rain-type-place, would be to get some air cleaner water shields (they look like inverted bread pans over the air cleaners) to keep the water out. Carey Hines sells 'em, or with very little tinkering you could make up you own out of plastic (Tupperware comes to mind) or aluminum baking pans.
A seldom mentioned fact is that the water shields also act as small megaphones making your lusty carb noises even throatier!!
gn