I don't fully agree with Tony that a D5100 is just as obtrusive as a D800 (especially if the latter has a battery pack attached). If you line up a D5100 against a D3 then the difference in body size is very noticeable. I will grant that if you tack on a 70-200 f/2.8 onto the D5100 then it does become much more bulky. However, most travelers who want to lighten their burden would be using smaller lenses too.
When I went to India last year I carried both the D5100 and a mirrorless camera. There were times when the mirrorless was a better and more practical choice. Most of the time, though, I used the D5100 with a 24-120 f/4. I never experienced anyone paying particular attention to the 5100.
Graham From St. Augustine, FL. "I like photographers, you don't ask questions." Ronald Reagan to White House Press Photogs