I have a sheet metal part that is built in and dependent on an assembly, making it necessary to extrude the base flange using a single line that follows a given profile. What I am wanting to do is then extend the part up to a given edge in my assembly, but I am not finding a functional way to do it.

The attached part is not the actual part but serves to illustrate my dilemma. The attached part has been built using the same process as the actual part. I used the Base Flange/Tab feature to extend out to the desired contact surface but it did not register as a tab and created a new body with a new flat pattern. 

I could edit the sketch of the flange but that overwrites the intelligence driving the mitered flange. I could model it using normal extrusions and convert to sheet metal but that seems to be doubling efforts and loses all the intelligence of the sheet metal features. I could use tabs to extend out the flat surfaces then manually modify the dxf to include the bend radius but I avoid doing that whenever I can.

I am hoping that there is some simple feature that I am overlooking that will make this easier.

This part and the assembly driving it are still being designed so maintaining the ability to drive the part from the assembly geometry is the goal.