ive never carried a wheel up there but i had about 60lbs of gear up there over about 700 miles... i noticed a difference in handling right away, my girlfriend (who drives the VX once a month or so) said she could feel the vx being a little squirrelier in turns from the passenger seat without me saying anything.. i think if you can make it work, keeping the spare inside the vx is a better option, but as triathlete said, many people do wheel with it up there, so it can be done definately.. youve ditched the backseat right? maybe a cargo box back there with a spare tire holder would be a nice mod?