I'm going to design a new X carriage for my printer, so this is the first thing I made, simply a plate with the holes in the proper places, which I expect may prove useful for anyone who wishes to design their own X carriages. All I did was take this thing (http://www.thingiverse.com/thing:170086) into Blender, delete everything except for the holes that I wanted to keep, then made a plate with some neat geometry. Should be pretty easy to edit from here (in Blender at least.)