I know you said you didn't want to take up boot space but here are a couple of options:
http://www.rallycodriver.co.uk/compcars23-f1.htm
http://www.motorsport-tools.com/inde...ex&cPath=17664
http://www.google.co.uk/imgres?imgur...w=1646&bih=858
It's a good idea to move the fuel tank as the original location isn't the best to put it nicely so to move it to the front of the boot space is a safer spot for it. You could remove the fuel tank and use that space to add a spare wheel well. Just a couple of ideas for you.