Lower Rear Quarter Patch Repair

A fair amount of massaging has yielded some decent results so far, however one area in particular I cant seem to get very close. It's where the rear quarter meets the rocker just in front of the rear wheel well. Pic attached.

It takes considerable (one arm) effort to push the quarter panel up so it sits flush with the rocker. In doing so, it appears to bow out the quarter away from the car, however I cant confirm as I haven't found a good way to keep it in place so I can step back and inspect.

All that being said, the new quarter sits perfect at the very lower front where it meets the rocker and door jamb, including the bottom of the rocker section where the quarter wraps under (front few inches only, then it gradually drifts down).

Now I dont think my rocker patch is very far off from when i cut out the original, as i had material on both sides to line up the patch quite accurately.

Any help on where to start looking? As expected, any adjustment makes other areas move out of alignment.

A couple thoughts:

-Could the new quarter be "flattened" a bit from hanging on my garage wall for a decent length of time, thus losing some curve and making it "taller"?

-The new quarter is for a 72-76 Duster so says the AMD box. I did check on their site that the same quarter is used for several models and years, but just triple checking here for sanity's sake.

-Is my car potentially that far out of spec from factory after 30+ years of hot roddin?

Any help is very much welcomed. 15232117353595541058577115119090.jpg