It's ok. I see. Of course dlls from SVP4 would be better.
I've read all your posts. The error in SVPFlow2.dll 2.0.3.0 is the same: Access violation in AvisynthPluginInit2.
Did you try SVPFlow1/2.dll from SVP4?
Your suggestions about video framesaize can be possible cause. It needs to be checked.
To make me help you: can you post your avs-script here?
If GDF4/5 are already work with Avisynth 2.6 then it is good!
I mean, it need to be updated to work with Avisynth 2.6 and with last versions of used Avisynth plugins.