The predecessor version of the Glass Goose, the SeaHawker, had an
interesting problem with flutter -- an upper wing could come off in
flight. This wasn't all that much of a problem, most of the six
aircraft on which this happened landed with no further damage. Don't
know if the Goose fixed this or not.

As for building at 120% -- no way. There are too many factors which are
second or third order effects to get away with this without really
knowing what you're doing.

Ed Wischmeyer