Great job and good write-up. My own meagre experimentation with small laser cut vinyl stickers had the same problem. And these were relatively small so not much surface area. So I don't hold our much hope. However the 'adventure' writing that comes standard on these tanks does work (paint?) so we know something works, just need to find out what that something is.
bikeless no longer! welcome home, 2011 KTM 990 Adventure!