End pin jack installation

[kww]

I've just purchased a K&K Pure pickup for my tenor guitar. It has a pretty typical endpin jack setup. The kicker is that my tenor hasn't got an endpin. I'm comfortable with the process of getting a 12mm hole into exactly the right place without doing damage. What I'm not comfortable with is the decision process of determining exactly the right place.

I assume dead center of the bottom is the right place for the jack. This locates the hole dead center on a visible seam where there a join between the sides. What exactly am I looking for in the interior structure of the instrument that tells me that drilling that 12mm hole is not going to cause damage to the instrument structure?

[Rroyd]

There should be an end block, 2 or 3 inches wide and an inch or so thick, visible with an inspection mirror through the sound hole, where the sides join. I have seen a few where the end block was little more than a veneer where the sides joined, but if you have a fairly substantial end block, you will have no problems. I always center them as you describe.