As long as the spare is snug against the tailgate and not flopping around you should be fine.
Some folks take the spare off and throw it in the back when wheeling, just to be safe.
In extreme cases, the welds can pull loose from extra weight, heavy jarring, etc. If you're worried about that happening, look into something like the Smittybilt oversize tire carrier (mfr #2743).
But IMO you shouldn't have a problem.