Bike Forums - Dahon Seatpost Length

Been looking into carbon fiber seatposts for my Dahon and realizing I really don't need a 600mm seatpost when 330mm or 13in are exposed from the seat clamp to saddle support bars. I recall 1/3 of the seatpost should be secured into the bike for road bikes, but really unsure about folding bikes. Anyone know what the apropreate length would be? I'm short for european descent and measured properly for bike fitting. I doubt I will change from my compact crankset I have on there and really want to be conservative with weight as I will be touring, but want to make flight requirements for luggage. Anyone know the answer I'd really appreciate the suggested length.