I would agree with your buddies. The only situation I know where up thrust is
useful is when the motor is above the wing. But, I wouldn't necessarily interpret
thrustlines of the real thing into what you need for the model unless you're planning on powering yours with a rotary of the same relative weight, and spinning a
scale-sized prop. As both of these things are pretty unlikely, I'd be more inclined to take my lead from thrustlines used in your average Piper Cub model than
how the original was set up.
> plane should have downthrust. Also, would anyone have any airfoil data on
> the wing?
Not sure what you're asking for here. Aren't the profiles shown on the drawings
you're using?
Cheers --- Larry