I have been following the Ultimaker and Zortrax for some time and noticed quite good prints consistently coming from both. Each appears to have a well built Z which obviously helps with layer alignment but I also believe there may be something to the gantry. Now the Zortrax went with a dual linear rod for each axis but I have been wondering, what about a MGN9 or 12 linear rail for each axis?
Has this been tried and failed for some reason I cannot see? Bolting the two MGN carriages together and creating a mount tor the hotend would be fairly strait forward and I would start by using regular 8mm linear rod for the belt carriage slides.