So in order to fix the Tip Rib I had to drill out the four rivets that were holding it and the l-bracket onto the spar. I had watched two videos on how to do this, each slightly different, and it looked easy enough. Well, the first one came out just dandy so of course the second one did not want to go at all, drill bit just danced around on the core. So I moved to another one and it was fine, then the last one wouldn’t budge. Various brute force tactics later and I got the rivets out with only minor damage to the holes, I will have to seek better advice for the next time I need to do this.
Anyway, turned the l-bracket around and re-riveted the tip rib in place and, as expected, the skin was now a perfect fit.