Agreed and I have considered that option. But for me, the second spare is an already mounted wheel (original 19") or buy another carcass. Plus I am thinking of situations where it is a long way between towns or farms. Admittedly that would be pretty remote trips but with having the second complete wheel ready to go, I think I might as well take it.
Taking only the carcass is definitely a better arrangement for roof rack load but a full wheel sees you up and going again quicker.
A carcass would solve my issue with lack of upper body strength :) and if that's what I already had, I'd just take the carcass but I think I'll stick with the full wheel.
Cheers,
Scott

