I'm comparing yours to the picture on the back of Spiderchain's DVD and it looks like your might be a teeny bit tighter. The chain should be supple enough to drape comfortably around the wrist. And the weave should be tight enough that the rings don't flop out of place.
Sorry - I don't know what size a Size 6 knitting needle equates to, but the other consideration is the gauge of wire you are using. The mm of the wire relative to the mm of the knitting needle = the aspect ratio. That's the number that will really tell you for sure if you are on the right track. It's O.K. to use knitting needles as mandrels but you will have better success if you create a little chart which shows you which knitting needles in combination with which sizes of wire will produce the appropriate rings for each weave you want to do.