I had always the problem that my Y Axis on my Velleman K8200 was not smooth. Problem was that the bearings were not straight in line as soon as you tightened the screws. This part solved the problem for me. Grabbed the idea on a forum but forget where. Please contact me if you like a backlink for your idea.
My X Axis was smooth from beginning, so... ;-)
Print this part two times.
I attached the bearings with wire. Cable ties will work too I guess ;-)