Straightening the sides of this mesh I'm having difficulty straightening up this mesh in Blender - see here for the object:





I'm trying to follow the accepted answer here but I can't quite get all the vertices I need in order to straighten up the side. When I scale the object along the z index, in 3JS, the arc of the sides is exacerbated which is undesirable.

Any ideas on this?

EDIT 

An example of what happens when it gets scaled in 3JS
Go into Edit mode.  Click the vertex-select icon.  

Press C for circle select.
Color in a couple vertices you want to align, then right-click.  

Tap S to scale, then X, Y, or Z to limit along one axis.
You have to decide which axis is best.
Then press 0 to zero out that axis.  

If you notice movement along the wrong axis, no worries,
just click X, Y, or Z at this point to affect another axis instead.
Tap Enter to finalize command.  

Repeat with each pair of vertices 'till complete.