Are we suddenly talking aerobatic control line here?
If so, a .15 will power a 2 lbs plane nicely.

@ Lou,
I always keep my numbers conservative.
In CL, I know my diesels vastly outperformed glow engines of the time. I was dearly disappointed by the performances of the OS engines I obtained in the 60-ies. They needed a load of nitro to perform anywhere near my trusty diesels, and then still would not pull a decent sized prop.