Ever since I saw some examples of carving out hollows by people like Walter Pall and Peter Adams, I've thought it's a great idea. I was just wondering if anyone could refer me to books/site/video that provides more insight into how to make convincing hollows.
One advantage to trying this, I think, is that it is a possible way to make a problem (like a big ugly branch in the wrong place), into an asset. But are there other motivations behind adding this feature to a tree?