I have it between two of my factory cross bars until I figure out how to mount it. I purchased a tire carrier which just isn't working for me as the hatch doesn't open with it installed. Removing it was a pain everytime you want to use the back.

Anyways, with that said, the spare is secure but I am worried the weight on the trail may damage the roof. The roof is the only sensible solution at this time as inside is jammed with gear usually.

Looking heavily at the KOR tire carrier.

 

Held my 36x14.5 I now made a conduit rack and that works to.

 

Was it on the roof itself?

 

It will be fine, the weight is distributed out pretty wide and evenly, plus it's not that heavy and if it was going to put a dent in the roof it would have done so when you put the tire on. But even if it did for some reason push the roof in it would pop right back out.