Try A different brand of rivot. I had this problem in trying to apply a mod to my rudders. The shaft would always pop before the rivot was tight. Oil worked great (for me). I purchased the rivots I used from west marine. Not the cheapest , but it got the job done. If your length is correct, then rivoting is usually pretty staight forward. You might try enlarging the opening of the inside of the rivot itself. Tap out the shaft and put the next size drill that just won't fit all the way through. then give it a try. Good Luck