Hi Frank,
Thought you might be feeling lonely out there so decided to post to show you that you are not the only one on PP that has a Volvo. Sorry can't answer your specific question but the tow hitch fitted to my 2009 XC70 is an aftermarket one (not original Volvo) and it seems to be okay. I live in France and have just bought the car in the UK so am a "newbie" as well.
Good luck, and you never know there may be another Volvo owner on PP who can answer your query.
