Go for the Airwild, MPI, or SWB arms. These will give you all the throw you need. Remember the longer the servo arm the more reduced the servo power. Here is one source to get your arms:
http://www.troybuiltmodels.com/newsi...servoarms.html
There is a lot you should do different when building a bigger plane; if you have questions please ask! Too much knowledge out there to be unsure on a first larger setup.