No personal experience of roof racks - always thought they looked ugly. That said, I wouldn`t have thought a properly fitted rack specific for your car would do any damage. The more likely cause of damage would be when you were mounting and de-mounting your bikes onto the rack. Pedals can make luvverly big scratches on lustrous paintwork.
Thats why I want a roof rack and not a rear rack, I think the chances of pedal touching the paint are a bit less if its t'on roof, or if it slips out of my hands when Im taking it down I guess Im buggered.
Dont you have a Foresester, dont comes with roof rails as standard?
Chris, I mean a trailer, not a caravan.

Im more of a shed man, than a caravan man.