Shims in the front band can help but that is not the solution to the real problem.
The gap between the barrel and the opening where it leaves the wood should be tight all around so only little more as that dollar bill I mentioned and not more or it looses it's support function.
It is also the reason why sporterized K31's with the stock cut short loose their accuracy.
When a shot is fired the barrel end makes a swing, a screw-on damper can reduce that but it is actually the task of the stock and the handguard.
Putting a shim under the tang changes the angle of the triggerhousing against the wood buffer in the stock to the left and instead of fully against it only the lower part of the housing is and this can result in a cracked stock in the lower wrist of a cracked trigger assembly housing in the rear top section.
Sorry for the text, I'm posting at forums in other countries like for example Switzerland also, the left arrow is pointing to the spot where it cracks when you play with the tang screw, the recoil forces should be spread over the complete vertical section and not on just the lower part of it.
In this drawing you can also see the shims inside the stock where the front action screw goes through.