Dont dent the pipe... Mine rubs too, it just grinds out the glass on it's own haha. or you can sand down the glass a bit where is hits to keep the scratches down a bit. It won't weaken the reinforcement that much. If it doesn't fit at all though, that's a different story.
This brings me to the thing that boggles me the most though. The pipe rubs through the fiberglass on the side, but the gas tank rubs through the pipe. I dunno. Just run it.