That never occurred to me or anyone else. Great idea. However, I've already committed to a fuel cell installation. I'm not happy about having a trunk full of gasoline, but this appears to be the most pragmatic way to move forward, having not heard of your solution.
The main two issues remain are the filler tube grommet. How to size that reliably is beyond anyone's guess. The other issue, that maybe the radiator shop could repair, is the possibly rotten metal at one of the screw holes for the sending unit. The grommet issue appears particularly troubling.
The odd "reverse siphon" effect that occurred when filling the tank up, and having it continually pour out liquid is caused by internal tank baffles, I am told.