I'm 210 and I always wear tennie runners up there and carry a foam pad to kneel on. There have been times when I had a lot to do up there that I pulled a 3' X 3' 1/2" piece of plywood up there to kneel on while working, just to spread the weight.
I've had both an EDPM (?) roof and a fiberglass roof, and in both cases I put up Eternabond. Check out my RV repair posts at my blog link below. And I'm convinced that it did a great job up there. But...leaks also come from the windows so I'm also using rubber RV gutters that are stuck on over the windows. Front and room windows. Then I'm using 4" vinyl tape covering the rubber window seals on the front window.
It's a never ending battle...but it's a slow motion battle.