Well it'd taken many weeks of head scratching, trying different things and at last it works.
I've ended up with a fixed track with 73mm heavy rollers at the lower part of the roof and floating garage door tracks at the top.
I would advise against doing what I did with a sloping roof , rather build the walls level then add a sloping roof to the Obsy.
The imbalance of weight versus gravity made it really difficult to get the roof to not try to slide down to the lowest point.
Anyway it now works, the motor drive works and all I have to do now is sort out the limit switches for the roof and extra limit switches to the Arduino to keep NINA informed as to where the roof actually is.
I think you go into these project with a fixed path to follow, well mine has more bends than Bathurst
Hopefully I can now get the rest sorted, security, power ( all 13.8vdc) and then instal some scopes
Cheers