Anycubic I3 Mega - Top Frame extruder support + Spool Holder

The Anycubic I3M Z-carriages are engineering masterpieces in terms of cost optimization (= reduction) but in the same time are the key features that affects the Ai3M printing quality. Whatever direct drive solution and fancy hardware one might install on Ai3M, the flimsy and wobbly Z-X axis will impact the printing quality.
Having this said, the RHS Z-carriage is particularly affected by the large stepper+extruder weight, mounted in an extreme off-axis position. The X-Z axis is even visually deflected and all the vibrations during printing are amplified by the RHS off-axis weight.

A minor modification - relocating the stepper+extruder in the top of the main frame - improves consistently the printing quality. Most of the time the filament deviation in the Bowden tube has also only half of the original (position) deviation and helps to reduce the filament compression and friction.
The introduction of the filament into the top horizontal extruder becomes comfortable, easy and less painful for the spine.

As bonus - a sexy hex spool holder can be used for a very short filament path using the default natural filament curvature. Even more, in the support there is a small storage provisioning - perfect for the removed screws, springs, nuts etc.

Installation - remove the stepper and the extruder (any model, does not matter) from the RHS axis, the metal bracket too; remove the top two screws keeping the clamp of the guiding rod; install the printed support, put back the two screws; install the motor with the extruder on it on the new support. The cables are long enough, use some ties to get a civilized look. You might need also a few longer M3 screws.

Edit1: Second version spool holder that might work with ball bearings 608 (Ø22mm outer diameter, Ø20mm shaft recommended) added. The colleagues KraliCzech has checked the first version - it was regretfully NOK and ver02 is corrected based on his recommendations - thanks again. Pre-post picture for modification added.

Edit2: Last three pictures and two models stl models plus one step file added for a particular case: extruder support fitting that might work with the RHS modified Z axis top fitting (included too).

The models added per edit are based on ideas from different users - see comments for more information.