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[serg]

DeSpot and FF3DFilter are not listed among available plugins in Hybrid's Avisynth

No clue what you are talking about,.. 
DeSpot is under "Filtering->Avisynth->Other->DeSpot"
FFT3DFilter is under "Filtering->Aivsynth->DeNoise->Denoiser" as 'fft3dfilter'

Cu Selur

Got it, just get lost in the different filters interfaces for Avisynth and Vapousynth.
May be it make sense to make them similar in terms of appearance.