After obtaining the original drawings of Vertex K8400 I discovered that number of things published here had mounting holes not perfectly aligned with the holes on printer's side and bottom panels. I corrected this and publishing today new STL files. If you downloaded old files and have not printed them, please get the latest versions posted today.
This is the second edition of my wire covers posted here http://www.thingiverse.com/thing:1504532
New covers look sleeker and contain shorter and simpler things than in the original design.
Thanks to Hae9wuum for suggesting to go without nuts. This suggestion was the main reason I decided to redesign the covers.
I rerouted the wires going to Z-sensor, Y-motor and left extruder. They now come up through the center hole of the bottom panel. I created a cover for these wires as well, however it is an optional piece.
Use M3x8mm, or x10mm screws to mount the covers. You will need 30 screws, or 26, if you do not intend to install bottom_under.stl.
I used infill 100% to make sure the areas around the screws are strong. This 100% setting, in fact, causes Repetier Host to crash. Looks like application bug. As a workaround I was saving .gcode files and then printing them from SD-card. It should be safe to use lower infill percentage.
All things were printed with touch-bed support. bottom-center.stl thing was printed with Everywhere support.
Before mounting the covers cut the threads by screwing in M3 screws into each hole.
Pushing all the wires under the covers is not an easy task; it requires lots of patience. Before tightening the screws make sure the wires are not stuck under the edges of the covers.
If you are installing bottom_under.stl thing, make sure the right-front screw does not touch the main board. M3x8mm screw is the best choice for this location.