Great, thanks! 
Fortunately, I’m not planning to use translucency in this case.
A tree I’m currently working on now has around 24k tris and it’s hard to make a single surface over it.
I think the main issue are the lightmap and UVs, I’m not sure if every single piece of geomtery should has it’s own UV space, or they can share the same one (the pieces are identical).
