2cm? Yep, your head was up there moving around like a you were a bobble-head doll.....
How do you steady a bobble-head? Use one of those U shaped inflatable neck pillows they sell for use on airplanes. Let's try that.....
Wow, this works much better than cheek pads. Inflate to the level you want and rest it on the stock. I found about half inflated was just right; nice and comfy and lots of support. Inflates in 2 minutes and useful for taking naps also.
I'll have to try this next time I go shooting.