The splined output shafts on modern servos have an odd number of splines. By fitting the output wheel in various positions when the servo's centered by the transmitter, you can get the alignment of the arms just where you want it. Usually, you'll find the arm just off by a small amount. Rotating it 180 degrees usually helps. On a six-pointed arm, just try each of the arms until you get the one that lines up.

Generally, even on the 2-pointed arm, one postion will be centered when the servo's centered with the transmitter control and trim centered.

You can check all the available specs of Futaba servos at:

http://www.futaba-rc.com/servos/index.html

You should be able to find one that suits your need.

Hobbico servos are made by major players, that's all that can be said.

(edit to fix typos)