Please re-read the OP. He asked specifically about drilling the dropouts. No one ever said anything about drilling the tubes, and if you look at the photos on the CL ad, the brake bridge is already setup with a fender mount that can be used for the top end of a rack. I agree that p-clips would be the easy route, but the dropouts look pretty beefy and drilling and tapping them wouldn't make the frame asplode from rust.