That's something I've tried to do: keep John true to himself, but back him up a decade to age 28, and strip away his battle experience.

What I did was I went to Joe Flanigan's early performance in season one, and then watched his performances when he was 27, in Family Album and Surgical Strike. He was playing different characters but I figured I could get a sense of his body language and, well, the "aura of youth" he projected. (I also watched, well, everything else of his I could my mitts on.) Surgical Strike was extremely short (we're talking seconds) but particularly helpful because it was a similar military role.