Problem with extraneous edges in adjacent sheet metal bodies

[calderp]

I am attempting to model a range hood with two sheet metal pieces that have spot welded adjacent flanges.

When I use the first piece to model the second by projecting the profile into a sketch plane and creating a new flange some edges of the first body are projected into my sketch. I have tried offsetting a line and still get the edges. These then create a false edge in my second sheet metal body, and a break. If I could figure out how to delete the false edge that would work as well as not creating it but I haven't been able to do that either.

I'm sure this is a very simple fix but I'm having no luck and I can't find any how-to videos showing this type of spot welded sheet metal construction.

[calderp]

The file.