JM,
Some (theoretical?) basics?
Our models
should have least drag when they fly as nearly tangent to the flight circle as possible. But where do we want that tangent point to be? And to what?
Simplest, if you think about it, would be to put the tangent point at the
CG and on the long axis of the fuselage, no? Our models fly at the edge of a circle. A straight fuselage axis, tangent at the CG, already has
some out-thrust angle (at usual line lengths, about 1ー or less. A straight fin/rudder (usually about twice a far aft of CG as the prop is forward of it) has about twice that: maybe 1.5ー or so. This is not large enough to really worry about. It seems to me, and has worked on all my recent models, to - at most - have the fin/rudder mounted basically on the axis but airfoiled with the curve ONLY on the inboard face. IOW, a slight lifting airfoil tending to cause nose-out.
If everything is just about right, IMHO the only reason for more engine offset on a profile is if everything goes slack, it will try to steer the model back out to full length of the lines. It is easy on a profile to slip a washer under the front mounting lugs, or a degree shim under them all.
Tangency can be created with adjustable leadout guides, which point the line pull's trail angle to the CG. If that's off, the pull force will try to yaw the model to make it line up. Complicates trimming... Also, this varies slightly with changes to the CG location.
Just some musings trying to see some fundamentals before the truly adept (in science, math, building, trimming and flying) share with us the fine details that they find useful, and might baffle many of us mere mortals...
/LOU