UPDATE 4/27: I still see a lot of folks downloading and liking this carriage. I'm glad people are finding it useful and it's still a great replacement for the stock carriage - especially if want to maintain compatibility with other parts designed for that stock carriage.
That said, there are better carriages available and I would advise folks to check out these other options:
UPDATE 11/14: Motor mount screws lowered 1.5mm. In the original the top of the motor could rub the 2020 rail if you tightened everything just right.
UPDATE 11/7: It's been pointed out that the top piece is almost the exact width of the rail slider and if you tighten the bolts it can push pressure on the slider and bind. I've expanded the part by 2mm (1mm each direction) to hopefully ease that pressure.
Here are functional replacements for the FT-5 X-Carriage parts (FT13 - top/bottom spacer, FT11 - back face, FT12 - front face, FT14 - cable chain platform). I tried to solve three problems with the originals:
1) They are melamine. They tended to warp, loosen, and crack. Print replacements with high infill.
2) The holes on the FT14 were not counter-sunk and the FT14/FT13 combination was awkward. This replacement combines those parts and has a pedestal for the cable chain end - no bending or warping. It also has nut-captures for the nylock nuts that attach the cable chain.
3) You needed a wrench to tighten the long bolts holding the FT11 and FT12 together. This version has nut captures for those nylocks as well. You can tighten up your X-Carriage with only an allen wrench.
Additionally, these parts should be compatible with the factory parts and factory-compatible replacements. I am personally using the FT11, and FT13/14 replacement from this set along with the FT13 bottom and FT12 from this fan duct set (white parts in the images):
I'd suggest high infill and using an extra perimeter or two for the parts with nut-captures.