Randomizing Tree sizes to a greater extent.

Well the other day I designed a rock, put it in the tree painter, and set the randomness to full, but it didn't variate that much. Are there any other methods that I should be aware of? I thought of creating a prefab with the starting rock, and scaling more rocks and putting them into the prefab, but is there a way I can make the tree painter think this prefab is one mesh?

Rocks shouldn't be painted with the tree painter. Unity has a designated detail mesh painter just for them. See here. Hope that helps some :).