4 usually denotes a Captain on civie street, which in a single pilot op, you are. 3 is typically a First Officer, or a Co-Pilot. If you are going to wear anything, wear 4. I was invited to a military "Flight Suit" party the night prior to an airshow and showed up with my four bars. I was pretty much the only civie there (in a navy blue military looking flightsuit (EMS)) and the four bars raised quite a few eyebrows. More than a few drunk drivers addressed me as "Colonel".
There was this engineer that got his hands on some pilots shirts with epaulettes and got some made up with six gold bars. He wore them whenever travelling in the third world, and got a suprising amount of respect.