A friend of mine who installs heating duct work showed me a neat trick once. They often have to drill through floor joists for fitting purposes. He used a section of coat hanger. Just cut it to length with a pair of diagonal cutters and chuck it up in the drill. It went through the floor joist quite easily. Now the wood in your guitar is most likely harder than a floor joists, but you can always test it out first.
Gipper