On the Drawing Board: 2 goes into 1

I've done small series before, 3 or 4 pieces that are alternatives of a common theme (Jock series, Sexually Implicit series, Natural Beauties series).  I've also done pieces that are kind of 'sequels to others'.  But my plans for my next project is to do a diptych, two paintings that work as one (connected by an imaginary 'hinge') while also being stand alone works.