I had been looking around for quite a while for a smaller hotend assembly. I had toyed with vertical carriages when I had wheel on the X axis, but once I got the MGN rails I ran into one big issue: most carriages don't seem to take into account that if you mount the E3D V6 hotend too far up, the nozzle can't touch the bed because the 4020 extrusion touches it first. So I found this nice remix but it had the same problem, the nozzle didn't touch the bed.

The hotend fan is a 40mm fan.

I modified the carriage mount to provide around 1-2 cm of clearance for the nozzle, just for good measure. The carriage seems to be originally intended for machines where the belts run "vertical" instead of horizontal, so I also added belt locks where needed instead of using the verical belt loop method. I did, however, keep the screw holes originally intended for this. You can use these with M3x10 or M3x8 screws to provide two small posts for cable strain relief on the carriage cables.

I also added a mount for the endstop switch. I'm aware that the switch hits the wheel instead of the acrylic, but on my case I just don't have the upper inner wheels on each side, I found tightening the X axis was far easier like this. Even if you don't take the wheels off, the endstop should trigger on the wheel, you'd only end up losing a couple of mm's worth of X axis.

The original carriage used a 5015 radial fan, I had a 4020 used for the Radial Fang fan so I just went ahead and modified the carriage lid to work with the 4020 fan. I provided the original 5015 files for the lid and layer fan in case you want to use these.

There's a version for the carriage lid with and without the BLTouch mount. There was no need for washers between the BLTouch and the carriage mount in my case. Offset for the BLTouch is: X = +34, Y = 0.

I included STEP files for everything that I modified.