Need help with biomes

I'm making a mod that adds about 7 biomes to my custom dimension, but I can't seem to be able to make them all spawn equal in size. For example:
Sometimes I spawn on a biome, do /locate to another biome that's 6000+ blocks away and then I teleport to it just to discover it was small as hell.

If anybody can think of a way to do so, then I'm all ears.

Something else that could be useful is if somebody could explain how the new biome system works, but only do so if you know, no pressure.

Thank you for reading.