I wonder what happens if you just drop the extent?
Is the provider actually doing a deep inspection of
the file (which should show that it is not what they
think it is) or are they going by the extent. Remember
that extents were a DOS thing, I remember when
you rarely saw extents in *nix like systems. That infor-
mation was carried in the file (still is for *nix like system
apps). Usually an extent as I recall was just to differ-
entiate, one file from another, but not to define the file
type.
Oh and add it back on if needed on the other end.