From on top of the camper you look at the rivet.
Place the drill bit on the edge of the rivet and where the rivet sits on the flange of the vent , not straight down as I tried with very little luck, Rather at a 45 angle.The drill bit bites into the metal easier with out rolling off to the side.As it starts to bite in to the metal aim at 45 angle to drill through the shaft of the rivet below the flange surface.The bit should be exactly the same size as the shaft of the rivet. If you aim just right the head of the rivet will come up and the inside part of the rivet will fall free. The best part (and to my surprise
)is the hole left in the skin of the camper is no larger than the shaft of the rivet.My new vent flange's pre-drilled holes did not line up with old holes, so I put a thick bead of silicone around the underside of the new flange pressed down to seat it then popped a rivet in each corner of the flange to hold it down straight and secure as I drilled and riveted the rest of the holes. I then wiped a little dab of silicone to the top of each rivet to make sure there was no leaks. I hopes this helps and thanks to the 86 year old black man that stopped, while passing by, when he heard me cussing on top of my Olivia, and told me how to do it right.
He said during the war(not sure which one) he repaired aircraft skins for the Airforce and this is how its done. I did get the silicone all over me,the drill, the drill bit, and the rivet gun, so keep a throw away towel handy to keep the mess to a minimum
NatchezBear