Biohazard
I decided that keeping a good tight seal could be better facilitated by having a smoother fill tube surface for the grommet to wrap around. I gently wire-brushed the crud off the tank end of the tube and followed up with some metal polish.
Unfortunately, this meant doing the whole thing. Particularly, the part that would be visible inside the trunk...
...and, of course, the fill port itself....
Its true...there is no shine like Mother's...
For those who didn't know...this tube is thick gage aluminum and polishes rather easily.
Looking forward to my floor pan seal coming in so I can put it all back together. You see, a fair amount of gasoline spilled out onto the gravel driveway and, as you would guess, it really smells foul out there. Once the tank work is done, I can push the Biohazard out of the way and throw a match on the wet spot and all should be well.