The first jig sounds like it should do the job but I would do a little bit more. Drill the bottom hole exactly the diameter of the base. Then cut a small, 1/8", strip away so the when squeezed with clamp it hill hold the base securely. Next, you should make a second jig to mark the top where the drill will start. Center punch it and drill with a Forstner bit. The bit will probably not be long enough so the drilling can be completed with a conventional long drill bit.