Used blender to create a cube, then applied subdivision and bevel modifiers.  Had to export to obj from Blender (2.66) as provided by Ubuntu repos which doesn't export to dae collada files.  Meshlab does import obj and export dae but haven't tested in rviz or gazebo yet.
This loads and scales the cube correctly.  The next step is to add a vertical cylinder to the cube in blender that will stand in for the joint.
The purely visual rotation joints are in the correct places and look good, I'll want to make sure gazebo ignores them except as collision volumes when I get to gazebo integration.  The other thing to do is make the segments thicker but shorter and the rotational joints smaller, since I want to put wheels on the segments.