Most of this mystery is easily understood if you build a few flat airfoil foamies. really light ones .
You can duplicate the old free flight "straight up and then flat glide" (tho much more of a rapid descent)
Just run the cg way far aft, to make the total trim for level flight ,power off 0-0 .
You should find that the relative AOA (whatever the airfoil -the true ZERO AOA) wing to stab needs to be tiny -and the CG- waaaay back. the wing and stab are sharing the job of providing lift.
The nice thing about using some flat foam is that if you screw up, a little quick CA and it is fixed for next test.
When I was a kid -we also threw FLAT wing, chuck gliders and folding wing AJ Walker gliders - best performance was aft cg /very low wing to stab incidence .