I've selected the Futaba 9650 for the rudder of the Lightning, modest torque but is within the calculated requirement (see Oli's servo torque calculator spreadsheet) and is high speed so as to optimise the gyro that will be used to damp out the swept wing dutch roll. At 15mm thick it just fits inside the Lightning fin so that only the servo arm and pushrod are exposed through the hatch.
http://www2.ripmax.net/item.asp?item...ry=060-020-010