After actually calibrating my machine, the results are MUCH better.  I still need to adjust the settings a little, but otherwise I’m very very happy with this result.  As you can see, the drawing is flipped.  Once flipped back, I think it is reasonably apparent this is Van Gogh’s Starry Night.  Here are a few things I’m going to try:

• The pen I was using seemed to stop working in certain regions of the drawing.  I bought a few new pens on my lunch break today.  Both are art marker pens – one blue and one red.  Unfortunately, both are too wide to fit in my current gondola.  For now I’ll use a thin sharpie.
• There is a slight curvature on the top and bottom of the drawing.  This is probably due to a miscalculation in the mm per rotation.  The downside to using a spool, rather than a sprocket/ball chain or gear/toothed belt, is that as the spool contains more cord, the diameter of the spool actually grows larger.  This means that when there’s a lot of line on the spool each rotation releases more line and when there’s very little line left on the spool, each rotate releases less line.  However, given the diminished space requirements, I don’t think this is going to be such a big deal.
• I mostly measured the machine width.  Basically what that means is that I did measure it, but then got distracted, then used what I recalled the width to be inches to calculate the width in mm.  Clearly, there is room for increased precision.
• For weights I’m using a bunch of spent batteries in a ziplock baggie tied with a wire to the gondola.  Too many batteries were causing the line to be too jagged.