I see a lot of servos sized by weight, 3.5g, 7g, 9g, 12g, they also give a torque rating 1.2kg-cm, 5kg-cm and so on. For a plane the size you are asking about, .15 glow power, you have tons of servo's to choose from. Analog, digital, plastic, korbonite, metal gear, plain, single bearing double bearing. You only limit is cost.
I have these in small foam planes to a 30 sized trainer, helicopters, gliders, glow and electric planes.
http://www.hobbypartz.com/9gexidimeges.html
I have a set of these, they are not a low cost budget servo, but not way over the top either. They have worked well for me in helicopters and gliders. Tough, fast, accurate servo.
http://www.hobbypeople.net/index.php...orq-servo.html
Servos have gone from only one to choose from, to so many you can go crazy trying to pick one.
Buzz.