I built the Contender with the flaps, standard wing tips, and powered it with the OS-46FX. Good flyer! By all means, add the flaps. Flaps add another dimension to flying. They are a lot of fun. As far as power is concerned; as mentioned mine is powered with the OS-46 and a fellow club member powered his with a .61. IMO the difference in speed wasn't much if anything. Save yourself a few bucks and less fuel consumption and go for the OS46.

DaveB