It is very low cost and improves your Ultimaker significant.
With 2 spools on the spool holder there wasn't enough clearance from load spring of the feeder to the spools.
The gearbox is about 20 mm high, for that reason I had to swap left and right hand feeder on dual machine.
With the first material loading I found that the feeders running inverse. (because I have swapped left and right hand version)
->OK no problem change firmware to get it right.
Printed some parts and made a material change.

I moved back in the material by hand and found it moves very easy.
What is the reason for that? I think it is because of the knurled shape on the filament, caused by the feeder wheel, is now on opposite side where is no pressure when moving forward.
https://www.youmagine.com/designs/belt- ... er-upgrade
Thanks to Meduza