Funny i just have to mention..After reading this thread a couple weeks ago, purchased a centering tool off e-bay for like 5 bucks, figured what the heck.
Last night I was installing a couple servos in a beater plane for snow fun, I carefully pre drilled 4 tiny holes in the servo rail with my homemade pin vise just by holding the servo there while free handed the holes and got one just a little too close to edge where it split while installing the servo hold down screw, today i'm sitting here at my computer looking at the new tool i bought still in it's packaging, I had already forgotton i had it, t sure would have been able to use it last night.