Size of Charcoal for applying into the soil - Terra Preta

This is my personal perception (hypothesis) about the size of charcoal which could be used for Terra Preta applications based on expereince and reason.
I prefer lumps of charcoal instead of fine charcoal powder, for the following reasons. Anyhow over a period of time the charcoal located within a depth of 8 inches, breaks during ploughing and other activities done in the farm.
- roots prosper better around a piece of charcoal.
- Soil microbes and soil fungus would find convenient place in a lump of charcoal and can live as a community.
- Lump can provide better environment and choices for soil microbes to thrive.
- Lump is heavy so less chance of moving away from the field due to wind / water
- Adds texture to the soil
- Additional energy is required to powder the charcoal lumps (which is saved).

There is need for testing these properties scientifically.

Thanks to bob klein(arclein) for the question.