The effect of props is a never ending source of wonderment .
The contra stuf adds more problems than cures-my opinion.
The rudder AND fin size n shape is a moving target.
The entire tail group is part of the TOTAL stabilizing force need -which -is another moving target.
Essentiallyyou need more stabilizing forces than the combined destabilizing forces.l
The compromises needed for a stable craft at some given AOA are not the same as those needed for a different AOA
You can easily prove this by flying slowly, inverted -and then upright.
FWIW- when the first of the big fiberglass IMAC planes hit the market - the tail wag was a common issue
adding a chunk of wood to the rudder TE was enough INCREASE in drag, to fix this particular issue . Those turkeys had more drag forward the wing than aft.
The old Quik Fli models -with the canopy placed ''just wrong'' had a annoying tail wag -
Fun Fly stuf with a cup attached to top of the fuselage -often flew with the same wagging
The turbulence was enough to reduce the stabilizing effect of the stabilizers .
Look at the whole model - each bit affects all the other bits .
- no math needed - just pay attention. -Β*Β*Β*Β*