I agree with Banktoturn, the most you can droop flaperons and still have good aileron response is about 15 degrees, and although this does produce considerable lift, it does not create the large amount of drag that you get from 30 degrees of flaps. Drag is a requirement for STOL performance. Drop the flaps, point the nose down at 45 degrees and the plane doesn't accelerate, pull out 5 feet from the ground and end up with a 20 foot ground roll. Now thats fun!
The reason I always increase the chord of the aileron is because the plane will be able to fly much slower than the original design, and the extra area keeps the roll control from getting too mushy and slow.