Jack,
I think you're totally correct about using the little spare with the oversized tires, but I'm talking about limping home if I had a blow-out. No highway driving, all back roads, and keeping the speed LOW. I would prefer to crawl home than leave my baby somewhere with a blown out shoe. If it really is that much of a problem maybe I need to rig up a mount inside so I can carry my full sized spare with me.
OR, maybe I'll do some major surgery on my garage door so I can keep the spare up top because I'm NOT leaving my baby outside over night.