Improved Frankenstein

I found that the LM8LUU bearings allowed quite a bit of twisting movement. I tried an experiment using two LM8UU bearings and stability of the carriage improved immensely.

Consequently, I have redesigned the bearing carriers to use four LM8UUs instead of two LM8LUUs. I have also redesigned the target cooling duct to have a single duct, the other arm now being used to mount a Tronxy square proximity sensor as close to the nozzle as possible (Offset is 38.5mm). The heatsink duct has also been r