i found that Grokster (maybe KaZaA too) needs the exact filesize to start downloads properly.
in sig2dat 3.5.a i modified the output - it now says i.e:
File: The Murmurs - Carry Me Home.mp3
Length: 2238464 Bytes, 2186KB
UUHash: =9gzWZsPi1v/Kq00YQ14VEVs83/8=
The length is interpreted correctly also by older versions of sig2dat.
so if you want post hashes for Grokster usage calculate them with
sig2dat 3.5.a.
(iMesh works with initial filesize 0)
indy