MVtools parameter set for MVFlowFps2 for blksize=4

[yup]

Hi folk!
Merry Christmas.
I try use MVFlowFps2 for frame rate conversion from 25 fps to 15. I use MVTools version 1.6.2, i read documentation for MVFlowFps2 function need use two clip, original and cropped for blksize=8,16 use crop(a,a,-b,-b) wher a=b=blksize/2 for blksize=4 need use crop(2,2,-6,-6) why not crop(2,2,-2,-2)? When I use blksize=4 i get worst result than for blksize=8.
script
DirectShowSource("fallenbob.avi")
source=SelectEven().LanczosResize(176,132)
backward_vec = source.MVAnalyse(blksize=4, isb = true, truemotion=true, overlap=2, pel=2, idx=1)
forward_vec = source.MVAnalyse(blksize=4, isb = false, truemotion=true, overlap=2, pel=2, idx=1)
cropped = source.crop(2,2,-6,-6) # обрезка на половину backward_vec2 = cropped.MVAnalyse(blksize=4, isb = true, truemotion=true, overlap=2, pel=2, idx=2)
forward_vec2 = cropped.MVAnalyse(blksize=4, isb = false, truemotion=true, overlap=2, pel=2, idx=2)
source.MVFlowFps2(backward_vec,forward_vec,backward_vec2,forward_vec2,num=15,idx=1,idx2=2)
with kind regards yup.

[Mug Funky]

you typically will get less meaningful results with blksize=4. that's the nature of it. with 4x4 blocks it's a matter of not seeing the forest for the trees, or at least not seeing the motion for the noise.

[actionman133]

I agree with Mug Funky: I get the most fluid results with blksize = 8...

[yup]

Mug Funky and actionman133!
Thank You for reply and advise. I decrease noise in source by MVDegrain2 and get good result with blksize=8 and overlap=4. In clip with 3415 i find at frame by frame seeing only 5 not very good frame, which i do not see during playback.
Happy New Year, yup.