Thanks,
perhaps i will stick to the roof bars, having had them for 9 year on an Audi i did notice that over time the rubber pads ever so slightly scratched the roof where they were clamped down. This was even when i only ever fitted then when the car was clean so no grit was under the pad. I also noticed that if I left them on the roof a long time the rubbers on the doors had impressions that took some time to come out after removal. Which was a bit of a pain...
With the rear mount I was thinking of getting some 3M clear vinyl where the feet went. But the rear carriers always look like they are moving around on other cars, but not seen a Saris in action, or the new Thule Raceway991.