Carrying second spare wheel on a VW Transporter is a dilemma for me. Inside the camper is not an option – there is not enough room and roof racks are not a practical option for two reasons:
I could not lift a wheel above my head and adding roof racks to my lifting roof is not a practical option as it is a fibreglass construction and I do not have the clearance under my house for racks.
The only options that seem to be possible are mounting a spare on the tow bar/ball or fitting it to the back tail gate.
The Hess Automobile product is possibly a better option as it allows for more rear vision if you only mount the wheel, but and also lets you store a second item on the back door.
Another tailgate mounted option is by 50degnord