Hi David
Just fit it centrally over the spare wheel, I don't think you should have any problem. If it is like the one NG supply with two hinged brackets and two wing nut brackets, use rubber tap washers under each 'leg' to protect the paintwork outside and a penny washer behind to spread the load.
Good luck.

Chris,
Thanks. All I wanted to hear was that it was straight forward and that there would be no surprises. I only have one day to fit the rack (which I have not yet seen).
Cheers
Dave

Enjoy your hols mate. Hope it's a tad cooler there.