A Note On Methodology
There are a few ways to add sheet metal information to a part referencing an external file; the trick when using 3D Interconnect is to add bends specifically using the Convert To Sheet Metal feature. Yes, the Add Bends feature will work initially, BUT if a new version of the part comes along that changes more than the part thickness, the update will not work.
Now that we have the preliminaries out of the way, I present the method I've discovered to work with sheet metal parts using SOLIDWORKS 3D Interconnect. If you try it, I'd love to hear how this method worked out for you.