I don't like the way the linear bearings are fixed in the Graber bed.
I designed this pillow block to hold the bearing and keep it tight.
It is pretty much simple to assembly and has captive nuts to make it straight forward!!
Print both top and bottom parts (you will probably need 3 pairs for your Graber bed).
Place the bearing inside one part, cover with another part and you are done.
For bed fixing, you are gonna need two M3x35mm bolts and two M3 nuts for each pair.