How to model a cover with a notch or relief?

Hi all,

I have a cover that is going to be 16 gage SST that has a notched or relief in it, although it will need to be also an weldment as there is not way to form it that I can think of I got both sides modeled just can't seem to get my head around how to form the blended area's attached is a few screen shots:

1: AutoCAD representation of what it should look like

2: the model I have so far

I have tried to loft the edge profiles together but with no luck.

The only other thing I can think of doing is a weldment, but seems like there should be a easy way to do this 

Any help greatly appreciated,

Regards,

SolidworksSheet Metal