i have built 3 identical wings for my 2 meters sailplanes.
they look alike and the only difference is that the last 1 has some spars of carbon fiber instead of spruce.
i can use them in several fuselages.
with 2 of them i have found that some times they flutter and worries me because the plane can loose its wings in any moment.
when gave them a closer look the only difference i could find was that the 1 that does fine has a turbulator at the leading edge (a piece of thread that is about 1/16" and runs at the neutral point of the leading edge).
so i added a thread at the leading edge to the 2nd and 3 threads at several positions along the chord to the 3rd and tested them today.
the 2nd with 1 string at the leading edge still had the flutters.
then tried the 3rd with 4 turbulators. no flutter!
then to the 2nd with 1 i added 3 more turbulators: again, no flutter!
so seems that turbulators not only improve the efficiency and stability but get rid of flutters too.
more tests to come.
now i got flutters again-that was with wing #3 and a short foamy fuselage. but same wing with 2 fiberglass/cf does fine.
need to do more tests. same plane flew fine after having flutters the day before. but also happens when the plane is going fast.
1 thing that i learned is that with the turbulators, the speed increases noticeably, so the more turbs the faster the plane. this may be good for windy weather, but as my goal is to thermal, are not what i need. they increase stability, but at the expense of loosing ability to thermal. you get stability in exchange of maneurability, and you loose sensitivity to thermals and the turning radius is larger. so, 1 thing or the other.

it is 1 of the things of the air, that takes some time to confirm your impressions.
(by the way, near the end of page 11 of this blog there is more on turbulators, if you want to see all that i have learned about it).