here is a very interesting article i came across
http://www.sikhsundesh.net/gurugranth.htm
where an anti dasam supporter is arguing with a namdhari over the issue of "wether gurgaddi was given to guru Granth Sahib Ji by guru Gobind singh Ji" the anti dasam supporter - charanjit singh bal uses sources to prove that guru granth sahib jis is the final guru that also support that guru gobind singh ji wrote dasam granth
i will post some extracts.... please see above link for full conversation It is interestign to note that the writer (charnjit) has similar views to dasam bani as the namdhari ha