First off we are only talking control surfaces so a standard servo is plenty for the throttle.
I try to match or exceed manufacturers recommendations no matter how I plan on flying it. Reason? I never know what the future will bring so it will be ready for anything I, or the next owner, will throw at it.
If 60 oz. servo is recommended then I look around for something reasonable. Example:
http://www3.towerhobbies.com/cgi-bin...&I=LXDTB3&P=ML
72oz. at 4.8v or 90oz. at 6v for $25 each.
Fair price and it exceeds recommendations.