That's one of the horrible space-saver spares, isn't it? I notice that yours is a significantly smaller diameter than the tyres you are running - which could make life interesting if you ever actually have to use it. :shock:
Mounting on the roof is an option, but you really need a secure platform (both in terms of being safely fixed, and not nickable), rather than just the roof bars when running a full-size spare IMO. The increased drag will also affect fuel consumption too, which may be an issue.
I guess you could bonnet mount it too, come to that - but then visibility could be a problem. :lol: