Lensfriend, the first problem I see with flaps is their set up. They need to be as crisp at the endpoints as Ailerons or elevator. Both ends of the flap need to be able to resist a finger push crisply. If it has any spongyness when deployed you will never get it to grove and always be on the ailerons. Read this thread, I think it will answer most of your questions.
http://www.rcuniverse.com/forum/m_34..._1/key_/tm.htm