You're right Andy, the vanes you added look great.

Thanks Richard. Good info as always.

Ram-Bro, the cowl of this model is molded with cowl flaps in the open position. Between those and the muffler exit, I think there might be enough air flow. 4 to 1? I don't think there is that much. There certainly is not 4 to 1 if you leave the full frontal area open. I'm adding a dummy radial to mine to close up a lot of that space. I think it'll fly better too after closing off what is essentially a big parachute up front.

Tom