Y Axis Linear Rail (Remix)

Updated Version is Here https://www.prusaprinters.org/prints/23893-y-axis-linear-rail-and-belt-system.

This is the first installment of my Y-Axis Upgrade. I have a MK3s but these mods should word on a MK3 just fine YMMV.

A Remix of https://www.prusaprinters.org/prints/5620-prusa-mk3-mk3s-y-axis-linear-rail-guide-upgrade.

When looking at the design I was wondering if there was a solution to mount the MGN12's with a precision metal to metal contact.

Goals:
-Produce the most secure mounting system possible for the MGN12 rails.
-Reduce parts counts as much as possible
-Printable without supports
-Any extra non-printed parts are easily available.

Changes:
-Decreased the distance between the deck of the rail and the 3030 extrusion to 3.4mm. Why? I found these precision spacers that are exactly 3.4mm tall and they can be secured to the 3030 rail with T-Nuts.
-Decreased the mass on the back supports. It is not necessary and the reduction saves about an hour of print time.

Notes:

-Parts count before the mod: 30.
-Parts count after the mod: 12 for mounts/spacers 2 rails 9 bearing mounts. Total 23! Each additional spacer support adds 3 parts.
330mm rails are now available (link below) so no need to get 350mm rails and cut them down. I also found a guy on e-bay that has genuine Hiwin rails he will cut to size with a price to match.

Update: 02/13/2020 As there are only two mounting holes for each carriage tightening them down while they remain perfectly straight can be a challenge, I solved this by using split nut washers that have a bit of spring to them for micro adjustments and I also put a M3x10 screw in the mounting hole on the right carriage that is exposed. I have been running these rails for a few days and the Y axis is near silent now.

Update: 02/15/2020 About every 10 prints I was getting a Y crash. I determined this was a result of a deflection in the rails. I tried two different scenarios. First just the 3.4mm washers. If I had more precision T-nuts I think this would have worked well but aligning the rails perfectly was a challenge. Next just the printed spacers. With just the printed parts the crashing is gone, it's slightly (very slightly) noisier without the washers but I'm leaving it as it.

Parts Used:
https://amzn.to/2OQd1N3 Amana 55367 3.4mm Spacer
https://amzn.to/2HkSHz6 MGN12C Small Carriage
https://amzn.to/31TXCjR 2x 330mm MGN12 rail with 2x MGN12H Carriage
https://amzn.to/3byJ8dL M3 3030 T-nuts, you will have a bunch left over.
https://amzn.to/31PTt0l Socket Head Assortment. You will need M3 10mm, 12mm and 14mm (I found the 12mm work better with the T-nuts) Socket Head Bolt.
You should not need to buy any bolts as you will have them from the original Y Rod Holders/spare parts bag.

Next Up: Y AxisTensioner and Motor Mount.

Print instructions

Prusament PETG 250/80
Prusa Slicer 0.2 quality with the following changes
Infill 100% (50% should be fine)
All patterns rectilinear.
YMMV