Render nether world on the bedrock

[Tonmyn]

How to render a map above the nether bedrock layer?

We have a lot of buildings in nether, but they are all located where Y is higher than 128. How can I set them up to render two nether map in Dynmap? One is to render the nether where Y is less than 128, and the other is to render the world where Y higher than128.