Combining Objects for Performance

I'm generating terrain with Perlin noise, creating large floating islands out of one object - a basic hexagonal pillar. The pillars are static and closely tessellated. An empty gameObject procedurally generates the terrain by Instantiating these pillars. So in Play Mode I wind up with well over 100 of these pillars. Basically, there are meshes on the inside of the islands when I really only need them on the outside. Instead of just combining the meshes, is it at all possible to make the whole set of islands out of one object that has these pillars, or even make each island an object? An image should be below. Tell me if I didn't include enough specifics. I really appreciate any help in advance.

VCobe