My goal:

Figure 1: The Goal
So, before I knew about the issue, her
A better solution:
values-12dimensions.xml file under values-12. values-12/dimensions.xml for the bottom left, and
bottom right corner radius.values/dimensions.xml for bottom left, and bottom right corner radius values, but remember to flip them.Use the dimension values when assigning corner radius instead of hardcoding them in your drawables. When a pre 3.1 loads, it will use the reversed corner radius values under folder values. When 3.1+ loads, it will use correct corner radius values under folder values-12.
Why is this better? You don't need to duplicate drawable code. Now you can change any code not related to corner radiuses without having to update 2 or more places.