Got a woodworking shop in town? Expensive gun and stock and I'd err on the side of doing it right. I did the exact same thing to a synth stock a few years ago. I was very careful but always wished I had had done a little differently.
My suggestion... find a shop that will do the drilling in a solid jig/vise with a very good bench type drill. THEN, (and you would probably have to do this part first unless the shop can help you) find a deep threaded insert and an appropriate rod and foot for the rod. If you use something like brass for the insert, it can be sanded to match the profile of the stock. To me, this is one mod that won't detract from value (might add to it) itfdone right. Screwing a pic rail to the bottom of the stock rarely looks good unless the stock is designed for it.
Just my thoughts based on stuff I failed at in the past.