I'm late to the party sorry but just a friendly answer to your question. I've been an A-10 pilot for over 20 years in the USAF retiring in the next couple years so full scale just like your Carbon Z or any RC plane use of flaps is essential. Yes it produces drag but it also produces lift specially if the nose is pointed into the wind. You are adding extra camber to the wing with flaps because you are changing the shape of the wing. Always use flaps on take off and once in the air level off gain airspeed then take out the flaps. Even if you want to descend use flaps as you can increase the angle to the ground without gaining air speed.
