The most difficult part of modeling this chair as precisely as possible are the creases and stitchwork in the cushioning.  I've done many, many models with difficult insets and piping before, but this chair presents some unusual problems.  The creasing on this chair happens to fall directly over each pointed edge of the chair, and then inside the edges surrounding the cushion (not directly on the outer edges, but inside slightly).  Simply insetting edges, or chamfering them, in this case, is not good enough.  Because of the convexity and angles of some of the edges, a quad chamfer with negative inset will result in crossed verts and scrambled edges at the ends of every corner.  Same will happen if you just use a negative edge extrusion.  So, I had to figure out a new way to create the creasing in this object, whereby the edges and vertices do not cross each other, resulting in a difficult object to unwrap.

It's a tricky bit of geometry, and in the end, the only way to do it is to fix the crossed bits by hand, which is time consuming compared to the overall modeling of the chair.

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