Well,I'm no expert-but we have cooked a few.
I assume you are cooking the flat and point together?
I assume you are cooking on a Cookshack?
Keeping in mind that when Jimmy Carter moved all grades up one level-to help the farmer/supermarket,etc???that moved all the "selects" into choice grade.
That left us with a huge variation in quality of "choice".
Could now be an 18 yr old dairy bull,or a longhorn living on desert and sagebrush.
Thin edges,will just be thin,and some comp cooks will just trim them to start with.
Have you cooked very many packers like this,to see if any are better than others?
Is there a particular brand you cook,as many meat plants have certain guidelines for their buyers,and cutting standards?
There are some brands that experienced cooks just stay away from,from past poor results.
Although,your approach doesn't sound bad,we rarely find packers come tender by 190º,even with a lot of resting time.
We may use the 190º,as a starting point.
Close to "Prime" could be exceptions.
We like to run the temp probe thru the flat in several places,and don't pull it off the cooker,until it passes thru almost like warm butter.
We may add a little liquid to the foil,while it rests a couple hrs.
Lo salt beef broth/black coffee,etc.
These could be starting points.
If you can,cook two of the same,side by side.
Cook one your regular way,the other with these couple of suggestions.
This might give you and us,a direction to head.
Hope this helps a little.