Bipes are not near as difficult to build and fly as some of the above comments imply. If you get the Sig Hog Bipe, you are almost guaranteed success and it flys like a trainer if you set it up with low throws. The biggest problem with bipes is that you must pay attention to decalage and build and set up per the plans, no shortcuts there. While more difficult to build the BalsaUSA series of Phaeton bipes also fly like trainers yet can be set up to be quite aerobatic as you progress in flying skills.