I had that squeak in my 2011 vert and after a little investigation I found the source. It is possible there are more sources than this one. In my case if I bumped the 5th bow with my hand I could make it squeak. If you lower the top just slightly you will see that when to top is fully raised the 5th bow comes up and stops against a rubber bumper on each side. The bumpers rest in brackets on the bow. The squeak I had was those rubber bumpers rubbing against the brackets when the top would shift. To verify that was the source I put a tiny bit of silicone grease on the ends of the bumpers and the squeak disappeared and never came back. Give it a try
John