As far as I understand the claim is that the deturbulator reduces the wings
profile drag, and there is no effect on any other component of aircraft
total drag like induced drag, fuselage and empennage drag, interference drag
etc...

I would like to see an overview of the drag components of an unmodified
Standard Cirrus at 51kts. Then we could discuss how much reduction of
profile drag alone would be necessary to achieve the L/D ratios of 45, 70
and even 100 claimed by Jim Hendrix in postings to this thread.

Please note that I do not rule out that deturbulators (or this specific
deturbulator) might have positive effects on profile drag, but I strongly
doubt the measurement methods used and conclusions drawn from these.

Michael