Flutter is determined by the torsional stiffness (and mass) of the wing
section. In this case, that did not seem to be compromised - i. e.
there were no diagonal wrinkles across the wing panel. If there were
diagonal wrinkles, flutter would be a real possibility. But dropping
the airspeed greatly helps the flutter margin, just as increasing the
max speed quickly reduces the flutter margin. I understand that during
each new aircraft's flight at the factory, the test pilot must dive it
to 110% of the indicated red line speed. The survivors are certfied.

There were diagonal wrinkles across the aileron panel, but I don't
think the aileron in itself can flutter. The question in this case
would be the aileron control integrity. Someone earlier suggested
blocking or locking one aileron. That could have all sorts of
interesting changes and very definitely I would not recommend.