Bolio! Thanks for the link. I should have remembered to look at his site.

AeroDave, what weight are you shooting for? Looking at Tower they say the GMS .61 will turn an 11x7 @ 13k. That's realistic enough to work from, so inputing those specs into ThrustHP (flawed, but workable) shows a realistic 1.6hp and 7.42lbs static. Using that hp rating, but changing props to a 13x4 shows a rather hopeful 13.39lbs static. These numbers sound like a 5-5.5lb airplane might 3D pretty well. How realistic do you think those numbers are?