The only issue I can see with this long term is the effect of the heat on the tire rubber. If I could create some sort of ally heat shield tray to protect the tire from radiant heat, would this be enough? Or would the convected heat still be enough to perish the rubber quickly?
Obviously it will require some experimentation and a bit of fabrication to make it secure, but I'm only willing to go to the trouble if its not going to shant my spare wheel.
And no, I'm not open to the idea of drilling breather holes in the bonnet

Cheers,
Tom.