While researching my active piezo dampening circuit for 17'-ers,
I came accross a lot of disputes about what actually works.
Apparently, most comercial versions have the winglets on 'top', while they know they work better on the 'bottom'.
The only example I can think of that uses a single sided winglet on the bottom is the U2. Probably a good example, because they did not care what it looked like, or what it cost.http://images.morris.com/images/lubbock/mdControlled/cms/2009/05/01/435251506.jpg
I seem to recall one reason they added top mounted, curved corner, winglets was for a somewhat self leveling property.
As the plane moved away from level, the effective upward lift of the lower wing increased because the blade effectively "got longer".
Maybe that's not correct.
The active piezo dampening circuit for 17'-ers was a bust.
So many parts that it required an 18' diameter circuit board that blocked the wind.
Which did make it quieter.