The question I am asking myself/agonizing over is whether to make that saw cut that you made in the existing stiffener, and if so whether to make several like the art of kerfing. I am worried about appearance. Or . . . perhaps for ultimately a better appearance, I should be more aggressive and cut into  the existing stiffener at the panel 3/4 chine line and chisel out all of the stiffener above the panel 3/4 chine (the ramped part) and replace it after I get the new stiffener (which I figure will be2a total length of 21 1/2″) glued in. That way I would end up with hopefully just a thin glue line between the old stiffener and the replacement ramp piece. What stimulated this idea is the fact that when I test bend the door (try to unspring it) it bends starting just above the hinge (at the end of the ramp in the existing stiffener) and this visibly seemed to affect the hinge angle (not sure why or if it matters). I guess the biggest reason is the thought that most of the offending spring back probably occurred under that stiffener ramp area. It wouldn’t be fun chiseling out that ramp with the headliner and gasket already permanently installed, but multiple cuts with my oscillating saw might help a lot.  What do you think Fritz, taking into account that my bevels measurements pretty reliably indicate that I need more panel 3/4 angle? The problem is that I “baked in” the spring back with the ramp portion of the existing stiffener so if the ramp is not removed the bending I introduce will be above where the spring back occurred (at least in theory as I invision it)???

Any opinions Fritz?