I wouldn't go digital on the rudder servo. If you're going to use a high torque on the rudder I'd use this servo and save $10 over the digital.
http://www3.towerhobbies.com/cgi-bin...&I=LXDTB3&P=ML
As far as the 6v battery pack I'm not familiar with that brand you suggested.
Me, I'd use this one.....you could fly all day on it!
http://www3.towerhobbies.com/cgi-bin...&I=LXNHS4&P=ML