The crux of the question really is "if the licenced and qualified engineer -
who would get paid for fixing the problem if there was a problem - says that
it's OK, does one trust that?

Do you trust the FBO? Why or why not? Follow the money.

Part 2 of the question is "why would full tanks cause this - why wouldn't
the excess get squeezed out the tank vents"?

That by itself, and no explanation from the "licensed and qualified
engineer" as to what caused it, would cause me to let somebody else be
the guinea pig.

Jose
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