Update 1/18/2016
I printed this carriage in PETG at 50% infill & have been using it for over a week without any problems. last night I printed a 14 hour print of a Delta Vertex. The carriage took over 5 hours to print. I included a photo of that carriage installed.

I modified this X-carriage design this past summer. I named it a happy x-carriage because it initially had a smile carved in the back plate. That design did not seem as functional as this, but it still seems happy. This was created with openscad. I used Draftsight to create the 2d geometry & TurboCAD to generate the ledge around the edge using the railsweep command. I have been sidetracked on some other projects, so I have printed out this final version, but have printed & tested versions similar to this. Thought I would go ahead and upload this in case someone else would like to try this part. With the added holes & triangle shaped cuts on the side, I believe this will help venting heat as well as cutting down on some vibration. I also added my x-carriage Belt clamp which is used by the openscad program when drawing this assembled to visualize potential interferences.

There are 3 main options for printing this part. You can add:

1. Ears to help keep it stuck to the print bed.

2. 1/8" brass bar cutouts to keep it stiff in case you want to try using PETG instead of ABS
   With the added holes for ventilation & the brass, my hope is to be able to print this in PETG

3. A cutout for ABL servo
   Dimensions for this were taken from clough42 part: http://www.thingiverse.com/thing:335632

Print one of these STL files or adjust the openscad file to your needs:
i3V_X-Carriage_rev30_repaired.stl
i3V_X-Carriage_WithEars_rev30_repaired.stl
i3V_X-CarriageNoEars_BrassCuts_rev30_repaired.stl
i3V_X-CarriageWithABLMount_rev30_repaired.stl

I plan to use 50% infill for this print.