Vinyl decals are clear coated all the time, and I think that is how the S-LSA RV-12's are done.
But I guess it is irresponsible of me to suggest that it will always work.
Use of a clear that doesn't use a reducer for spraying is recommended.
Also, a spray test with the particular clear and vinyl you intend to use is a good idea.
Do a google search on clear coating vinyl. There is of course some info saying it can't be done... there is a lot of info showing it is done all the time.
I agree that using a paint stencil is the best way. It allows using the exact colors that you are painting, but there is no stencil available of the RV-12 logo.