Thanks Andrew,
Got it working now. I think it was down to the power requirements for running 2 VSGs from one hub on my dev laptop. I successfully got it working yesterday with 1 VSG and 1 SM200 running from the same usb3 hub. And the other vsg plugged into a seperate port. The SM200 is not bus powered.
All works fine now. I hope to try 5 devices today.