The OMP 65" Yak54P claims to be 7lb. A Saito 91 will pull that fine. I am a little more power hungry, and will likely try the Saito 100 in that same airframe someday. Right now OMP only sells 65" Yak kits, but they claim to have an ARF version someday soon.

If you want high thrust:weight, get a 40 sized profile like tiktock. One of the columnists from RC Report claims to have a 91 in a CG Ex-treme 330. I have a 72 in the same plane, and it could use a little more power for my taste. If I were to do it again, I'd go with the 91 in it too. I must admit that my Ex-treme vibrates like a sumbich with the 72, though.

Hope this helps,
Kurt