I had a leaky seal, replaced the seal last year and it still leaked. When I had installed the filler neck tube it slid in pretty easy and my friends all told me it should be hard as hell. This winter I bought a new stainless tank, grommet, and filler tube and had a heck of a time pushing it in (this is an understatement). Grommet ID was 1.855 and my tube OD was 2.025. After several hours of blood sweat and tears (literally) trying with Vaseline, dish soap, freezing the tube, grommet in boiling water to soften it, I came to the conclusion it wasn't going in the way it was. I took my filler tube to the belt sander and put a 1/4 lead in on the end of the tube. I then took some emery cloth to take off the edge and make sure it wasn't going to cut the seal, lubed it with Vaseline, and it went right in. I couldn't believe the difference. Now I have my fingers crossed it won't leak, it really shouldn't. The design of a rubber grommet/fill tube into the bottom of the tank was not one of their better ideas....
