Geat. It looks closer than previous using input size 2x81x81x81x1 and your kenel size suggestion
tensorflow result 0.05861372 
Pytorch result 0.029243657

However, the code also uses
win=[kernel size] * 3
win_size=np.prod(win)

So if I use kenelsize is 4, then it will be change the result on np.prod(win). Do you think we still need to keep same value win_size for both tf and pytorch, ie 999 and just modify size in the conv3d?