My son is using the Hitech blue 9gram servo in his four pound, sixty inch span J3 (it's fast) and has been working ok for a few years. Probably has about the same servo loads your ship would see.
I'm electrifying an old Geebee Dreamer, a forty powered four and a half pound biplane that's very hot. and I'll be using Hitech H-81s in it. They have a good bit more torque and seem to have a smoother gear train too.
I can recommend both depending on whether you want low cost or pay a little more for a little insurance.