Thanks for the comments folks.
I would like a 7 metre run that is reliable.
I've tried a number of different 5m long passive USB3 cables, one 10m active cable (with and without power to the camera end) and a 5m passive USB3 cable into an 8 port powered USB3 hub mounted to the scope.
I use Dell Precision M3800 laptops (a model introduced in 2014) and I dont believe there is any issue with the 3 USB3 ports this model provides.
What I was hoping to discover was whether anyone of you folk have a specific hardware solution that is known to be reliably capable of a 7m stretch.
Thanks.
Tony