How do you create biomes for an end generation type dimension?

I'm working on a simplified version of the Aether mod that basically only adds the generation and no lore. I've chosen the end generation dimension type.

I have 3 biomes, 2 forest ones and one plains one, and I can't figure out how to get them all to generate properly. I've been changing around the values for the past few hours, but all it seems to do is either make only one biome generate, or generate all biomes but two are in the void (so no blocks spawn.)

Does anyone know what values I should put into the generation range parameters to make all the biomes generate?