I'd still consider removing the lens mounting rings, anyway. That way you both really don't need a drill press, and also aren't filling a tube of metal with drill filings that will subsequently share air with your camera's sensor and works.
(Did you catch that bit, by the way? When you drill, you make metal particles. Trying to make a straight shot through both lens and camera mounts may or may not damage anything in between, but it's far better to take em off, mark correct locations, drill far from your optical equipment, clean with oil, *Then* do your soldering and reassemble. Bonus is, just cause something may actually be in the way between doesn't mean you can't still thread a wire.