I thought I was being very carefull, knowing the potential for problems. Still happened anyway.I :agree: with a large emphasis on being "careful when filling up".
Luckly the flapper had just come loose internally. I guess you could call it "lucky" in the bigger picture.
With some help and ideas from Pro_GT driver, I think (finger's crossed) I have improved the catch that holds the flapper mechanism in place and won't have to pull this out again for a while.
Now I just need to get it all back together this weekend and get that *@^*&* fender liner back in place.