Personally I would go with
Leo on its own, because I dislike most (all?) of the names that can be shortened into
Leo. I've known
Leos (full name) my whole life so I guess I don't see as nny as others do, although I can understand why some people may see it as such.
“It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.”
~Mark Twain