Huge technical difficulty already...

After much testing and messing around with the Xtras folder, I look back on the Smoothware website (http://www.smoothware.com/compatibility.html) to find their "compatibility table". And lo and behold in black and red there is...

The Bad News:

DV FireWire Cameras

so our finely laid plans to run one USB webcam and one FireWire MiniDV camera on a single machine have gone up in smoke.

So either we use two separate machines networked together, or I find a clever way to run two USB webcams on the same machine at the same time...?