I thought that I had a leaking fuel tank but then, after freaking out an examining it in detail, I finally realized that I had to be really careful when filling it as if fuel spilled into the ring around the opening it was not draining and it blew out all over the place when I started to ride off. Now I have become very careful when filling the bike and there are no more issues with fuel drenching me. I also do not try to fill to the absolute brim as I get good fuel mileage so it has decent range.
However, you say that it sloshes out, and that you see evidence of a deformed gasket, so that sounds like a different issue. I only mention what happened to me because it reeked of fuel and also got fuel all over me a couple of times. It turns out that a little overflowed fuel goes a long ways.