Can you reduce world height?

You can change dimension_type/overworld to increase and decrease world height, but I want to also shrink all of the material layers (so there would be a very thin stone and deepslate layer before bedrock). So the bottom of the world would be at around Y=30 with thin stone layers on top of it. I know you can change some of this in noise_settings but my datapack fails to validatate when I try. Is it not possible or what am I missing?