I decided earlier to take the extruder off the push-rod.  It just added too much mass for me to be happy with it.

But with a little trickery here, I believe I can keep the same length bowden tube by hanging it from one of the octahedral rails.  

This requires that it can pivot freely though.  To pivot freely, the pivot point has to be on it's center of mass.

So, I made a new extruder mount.

For now I'm just going to hang it with a wire hanger.

Hardware source updated in Github.