Not realizing that 4 of these stainless rivets on each side of the bottom skin, should have been left empty till finishing the exhaust tunnel, I was happy to get the entire bottom skin riveted on. So, now, I had to drill out 8 stainless rivets, 4 on each side. I was successful, thru much pain and strain, to get the 4 on one side out. This made me think, there must be an easier way. I know that drilling thru stainless is very easy on a drill press, and not so easy pressing on a drill. This thought led me to the conclusion that I needed a drill press that could drill upside down. Here is what I came up with and these 4 rivets were out in about 5 minutes, with no strain nor pain.