Wood can swell quite a bit cross grain, but not so much so length wise.
I've restored a couple of Chris Craft runabouts. After years of being in the dry Colorado climate you could see through the gap's in the planks. I would have to soak the boats hanging from a hoist in the water for a week or so and they would swell back to being water tight again.
Here's some thing I've thought of trying on a stock head that has that the metal proud of the wood. First get all of the oil out of the wood. Then soak the stock head in water until it's just proud of the wood and then wick superglue into the end grain of the head and see if that wouldn't keep the wood expanded when it dries.
Just an idea. I've never tried it.
