Create an opposite-hand mirrored assembly without creating mirrors of each part

Hi,

I have tried selecting/deselecting the individual parts, changing orientations, selecting "create opposite hand", etc... But haven't had any luck.

The parts themselves don't required opp-hand mirrored versions.

The gusset plates on the back-side are patterned.

Only the assembly and mates need to be mirrored and the pattern direction would need to be reversed..

I have attached some pictures.

Any advice on how to make it work?

For now I have just manually made a new "mirror" assembly as a configuration.

SolidworksAssemblies