However, this summer I did have the mylar on the lower
surface of one wing give some problem. The 'safety'
tape kept the mylar from leaving the ship, but the
mylar somehow broke away from the double-sided tape
and it rotated 90 degrees, more or less and was perpendicular
... So, how did the mylar rotate 'up' and create
the spoiler, even though the leading edge of the mylar
was taped to wing? Why didn't the airflow keep the
mylar pushed down against the wing?

Guessing he no internal seal of the aileron, or seals between
fueslage and control rods. Then, high pressure from the cockpit
ventilation escapes out the aileron hinge line. Add to this a
separation bubble forming just in front of the aileron hinge line so
the air isn't moving there anyway. If I'm right, seals and zz tape
would give a different result. But of course the mylar will be glued on
tight so we'll never know...

John Cochrane BB