I've had two of the 84" Wild Hares and still have the Extra. Both powered by a Brison 3.2 and fly well.. If the BME comes in that light, why not go with the BME engine. It's said to have more power than the Brison, but who knows. It is lighter for sure. In any case, the firewall and instructions will most certainly be set up around, show, and have mounting instructions for a BME 50.