The Reese Dual Cam HP that I bought, had self tapping bolts. You need a punch to start the drill location because the bit will fly all over the frame without a punch. From there, after the hole is drilled to spec, I applied some silicone caulk to the threads, head and brackets to seal any water out as I torqued the bolts down.
So far, the brackets have stayed attached and I've been happy with the dual cam, particularly since going to 600# bars with our Safari. Remember, you need some flex of the bars for the dual cam to work properly.