This Hilson is curve drilled. I have a flexible drill bit for lapidary, but the end bit is busted. Skip Elliot has had one made especially for drilling curves as well. It is a flexible shaft down a hollow curved tube with a bit on the end for chewing through the wood or stone. There are more available for masonry and lapidary work than woodwork, but they are out there.
BTW, I have only smoked this pipe about six times, and I am contemplating letting it go. It just doesn't suit my clenching style, but smokes very well. I am just not comfortable holding a pipe. If anyone might be interested, PM me. We can barter in private. But, I would accept a more than fair price.
I bought it mostly for the novelty of the curved drilled draft hole, which quickly loses it's novelty if you have to hold it.