If you haven't already built your battle floyds, i suggest you use a HARD balsa spar, or pref a piece of yardstick for the spar. I built mine thinking i would use a 15, ended up using a BB 25 and the balsa spars cracked. The BF flys great but is not particularly tough, i would suggest adding some strapping tape to the wing at the LE and spar, also some reinforcement to the fuse.