How to remove layers and adjust thickness?

[Morphlng]

Hi! This work is of great help to me, but I'm a little confused since the lack of documentation.

1. It seems like the rendering layer is based on the BirdViewMasks static class. If I don't need some of the layers, e.g. traffic lights, should I simply comment them out or I have to change some other code?
2. I want the center-line to be a little thicker, I saw the thickness in lines.py, but adjusting it doesn't seem to work at all. Why is that? And can you please expose an API to make it easier to adjust the thickness of some layer, instead of directly modifying the code.