I built a few Twisters, all powered by FP40s. Midwest Magician, Walter Umland wing kit. Lengthened moments, slightly enlarged flap area, elevator/stab, increased 30%. Powered that with a Tower 40. Light weight, 34ounces total with engine and tank. Flite Streaks, Galaxy.The Magician flew at the NATs when rain and wind grounded many. All these engines use free flowing tongue mufflers. The Tower 40 in the Magician used a .272 Lee Venturi, one or two extra 10 thousand head gaskets. Powerful stunt run. Available 25s do not pull these planes with similar authority.