I like the dirt stained knees. You might want to consider getting your hands a little dirty. I've never been a reenactor, but I was on a few camp outs with the Scouts and we weren't afraid to get our hands dirty. I feel that you have some outstanding advantages because you are young and thin. You are probably much closer to the average Civil War soldier than many or most in reenacting today. You look very approachable so if you do living history you might get more questions from kids than other reenactors. You might help build a new generation of reenactors. I see lots of potential in that smile of yours.