Wanted to try the PETSFANG DUCT for DIRECT EXTRUDER (Thing #2907538) but there was no fixing base for the U20...
This base uses 4 fixing points to the carriage! Very solid... :)
Get the other parts from the original author.
Please note that you might have to adjust your Y axis zero as the base is thicker than the original.
I also splited the part in two (that's how I printed mine -> super glued and screwed) to have less supports and better orientation (strength) in the upper part where the motor is fixed. Up to you how you want to do it! :)