5'6??
Hell, I'm 5'5"!! 
Yes, you can pull it off. It's much more acceptable to be a 5'6" Fett than a 5'6" Vader.
I do haunted attractions every year, so the study of the psychology of people reacting to you while you are in costume is something I've spent many years exploring.
(Do you have any idea how many people poop themselves when confronted by an evil clown? You'd be amazed.)
There's a definite science and methodology to knowing how to properly take advantage someone else's "personal space" while you're in costume.
Most of the theory that I've discussed above really only applies to "masked" or "helmeted" characters, though. If you dress up as Han Solo, people can see that you're obviously NOT Harrison Ford. Therefore, you are really only a "representation" of that character. But when your visage is hidden behind a character's helmet or mask, you ARE that character. So you gotta play it straight up.
~Brian