This mod has all plate combinations for mounting MGN12H blocks.

You can use two main configurations:

• Single Rail
• Double Rail

In Single Rail configuration there are plates:

• 2 MGN12H Blocks
• 1 MGN12H Block

In Double Rail configuration there are plates:

• 4 MGN12H Blocks
• 3 MGN12H Blocks
• 3 MGN12H Blocks Mirrored (Horizontal, left and right, mirror)
• 2 MGN12H Blocks

NOTICE - WARNING:

• This is not complete installtion walkthrough and whole part list.
• You lose some Z height with this mod!
• Using 1 MGN12H block on single rail is flimsy and makes bed oscilating too much (I tried it for the kicks and it didn't work)!
• In configuration where I list 400mm rail I did not test this. 400mm should work, but not confirmed.
• When screwing endstop, don't overtighten! It can break.

This mod should be classified as EASY.
There isn't much dissasembly and fine tuning. Also only one printed part needed and simple screws and nuts.

Linear rail part list:

Single rail - 2 MGN12H Blocks:

• 1x 450mm or 400mm (400mm should work, didn't test) MGN12 Linear Rail
• 2x MGN12H Block

Single rail - 1 MGN12H Block:

• 1x 350mm MGN12 Linear Rail
• 1x MGN12H Block

Double rail - 4 MGN12H Blocks:

• 2x 450mm or 400mm MGN12 Linear Rail
• 4x MGN12H Block

Double rail - 3 MGN12H Blocks (also mirrored):

• 2x 450mm or 400mm MGN12 Linear Rail
• 3x MGN12 Block

Double rail - 2 MGN12H Blocks:

• 2x 350mm MGN12 Linear Rail
• 2x MGN12H Block

Installation tips:

Endstop - You don't need to move endstop. Just unscrew it, use larger M3 screw, 2 washers and eccentric spacers you removed from carriage wheels. 

Use this order Washer-Eccentric spacer-Eccentric spacer-Washer-Endstop.

It will be perfect height for carriage to trigger it, just as it was before.

Linear rail mounting - You need assortment of M3 6mm screws and M3 T-Slot nuts. You don't need to unscrew M5 screws in the Y extrusion just don't use M3 screws in that place on rail.

Linear rail aligning - Move rail/s all the way back on Y extrusion. Mount the blue bed plate on rails and move it till it "clicks" on endstop in the back. Now you know how far they need to go in the back. Move rail/s toward front till you can feel with you finger it is on the edge of MGN12H block on back side. Make a line with pen on extrusion so you know where rail needs to go, after proper alignment.

Printing mount plate - 
60% infill
PETG (PLA or ABS also works)
0.3mm layer height

Belt - Stock belts can't be used. They are too short. You need longer belt GT2.

Belt mount - Original belt mounts on blue plate can't be used. You need longer screws on the plate (40-45mm) and belt will be mounted on them.