I finally came up with an extruder I am happy with. Open design, easy access for cleaning, loading, unloading, etc. This version will mount to my 300mm No Sag upgrade.
I have been running this on my machine for a few weeks now and I couldn't be happier. Have not tested with the Ubis hot end. It will fit, but I am not clear about the amount of heat that transfers up to the mount. This works very well with an E3d hot end.
I re-used the spring and screw from my stock Printrbot wood DDE.
My spools sit next to my printer so I also included the filament guide I am using that attaches to the 300mm No Sag bearing plate.
Poor documentation, so any questions please feel free to ask.
2014-06-24: Added a front end version "JL-DDE-Simple-Double.stl" to work with the Double Precision mod: http://www.thingiverse.com/thing:344822
2014-07-28: Uploaded a revision to the extruder to remove the cantilevered bearing post. "JL-DDE-Simple-Double-2014-07-28.STL" & "JL-DDE-Simple-2014-07-28.STL". This should help eliminate bearing alignment issues if the part experiences any warping from extruder motor heat.