Modifying World Max build height and min

Hello, I pregenerated a world with Larion world generation mod, and I removed it (and limited the world so no new chunks can generate) How could I potentially make a datapack to keep the world set to -128 min and 512 max, since I wont be generating new terrain, it shouldnt be an issue? Here is my code, I tested it in a single player world and a world with larion and it doesnt work, any help would be appreciated. { "ultrawarm": false, "natural": true, "coordinate_scale": 1.0, "has_skylight": true, "has_ceiling": false, "ambient_light": 0.0, "min_y": -128, "height": 640, "logical_height": 640, "infiniburn": "minecraft:infiniburn_overworld", "effects": "minecraft:overworld", "bed_works": true, "respawn_anchor_works": false }