Exported STL looks distorted Blender 2.77a

Problem

When I export this blend, external software shows it as heavily deformed. Blender shows it fine and so does the Windows Object Viewer.



Shapeways and Tinkercad however shows the following:



I've tried to export stl, obj and other formats (ultimately I'll need stl) and they all come out the same. I have tried to convert quads to tris, but that did not produce a different result.

Object is manifold, has no loose geometry, no doubles and no pending modifiers.

Anyone know why and how to fix it?
I suspect this has something to do with the size of your object - perhaps the images we are looking at are at least 400% bigger than what you hope to print? If that is the case the image might look distorted but is correct for the resolution that it is actually printing.