The recommended motor doesn't look suitable at all. The motor is designed for fitting behind the firewall with the shaft sticking through. The Edge is designed for the type of motor that bolts onto the front of the firewall with a cross-mount. A few people have commented about this problem in the discussion topic for the Edge.
This motor seems like a much better match: http://www.hobbyking.com/hobbyking/s...ner_Motor.html
Either 3 cells with a 13x7 or 14x7 prop or 4 cell with a 12x6.. should go great!