I'd use the JR 9411 Digitals. Mid size coreless-- 82 oz. torque at 4.8V

You could try the JR 7005 coreless, but I'd be afraid the gears weren't strong enough. I had a pair that I was going to use on my elevators of my 27% Extra. I took the cases apart and looked at the gears, then decided to use the JR 8231. Not a mid size servo- but 88oz. torque and bigger gears than the 7005.

Also look at the JR 911 servo. It's a mid size 5-pole motor. Better than analog, but not quite as good as a coreless servo. I'm usung them on a 40 size 3D, but it's OVERKILL at 6V. They are 42oz. at 4.8 V

Also look at the JR 9011 mid coreless. 60oz. torque at 4.8V.

Try this link. I've got it saved in my favorites. It lists almost all the current JR servos. Not always the cheapest place to buy them, but a good reference when searching for the right servo for a given application.

http://www.centralhobbies.com/radios.../JRservos.html

Stick with the JR servos-- your plane will last longer. I tried Hitecs on a couple of planes. Got the toothpicks in the landfill to prove it.