I've tried but, I was not completely satisfied. I couldn't get the noodle properly fixed in place. So I'm here for the tips, tricks and recommendations too.
Tape measure. Kallax is 33.5cm, I cut at 34cm. Then it slightly compresses the 2 ends. Will really only work if you can get your unit fair close to the wall.
Here is a pro tip. If you are one of those people who puts the boxes from boxsets away in the closet, try putting one at the back of the cube. Different widths, but those Bowie boxes work great.
Pro tip. Make them a little long. They dry up and shrink in the winter. I ended up tacking a thin piece of wood trim across the back with the noodles wrapped around the wood as a cushion.