I find myself in the unusual position of disagreeing with WillWagner.
Running thimbles alone is generally a bad idea. Here's why-
They weren't designed to be used by themselves and require the outer lug nuts as reinforcement to have the neccessary strength.
The above implies that you could just add the outer lug nut to the thimble and be ok running just one wheel. This isn't the case. The outer lug nut needs the thickness of the 2nd wheel in order to work correctly as reinforcement to the thimble.
Running thimbles by themselves is illegal.
I've seen it done. I haven't seen one break. I have talked to other people who have claimed to have seen them break.
As for me, when I convert a truck to singles, I also replace the lugnuts to the kind that are in the front. Running thimbles alone is something that I would do to get a truck home, but not something I would do as standard operation.
Unloaded and mildly offroading, you'd likely get away with it. But I don't advocate it.
