Jeff-
Sam Turner showed me how to do this a long time ago. First, use furniture dowels. They have a knurl that is easier to adhere to than the pushrod type dowel material you find at the hobby shop. You can chuck the dowel up in your drill and put in a really straight, centered hole with a little effort. Use a piece of brass tubing modified with some teeth to cut the hole for the dowel. I find that they’re a little softer for that touch-up sanding, too

Troy-
Boy, do I like ball-bearing horn pivots!
Unfortunately, I’ve been disappointed in the horn stanchions being produced and marketed as high-quality, high-ticket items. They leave a lot to be desired. You state that the MKs you’re using put the pivot point over the hinge line. They do not. You, the builder put the pivot point over what you *think* is the hinge line and *then* hope that you drill the holes in the right place. So there’s at least two places where accuracy can be compromised.
Even as an experienced builder, I feel Jeff’s frustration. I went through this when setting up the pull-pull on my Smaragd and trying to get good equal tensioning with slightly misaligned holes. Perhaps you read my article at http://www.mindspring.com/%7Erellis2/rcpattrn/ppull.htm .
What’s sorely needed from the manufacturers is a nice horn stanchion that is adjustable in two axes, height for throw magnitude and fore/aft for equilibrium.
Maybe if you don’t use P-P, it doesn’t matter as much ‘cause you can ATV it out, but such a horn would make a lot of people like Jeff and me very happy and more willing to cough up the six to nine bucks for it. Maybe you can stick a bug in Central’s ear for us.
-Ron Ellis