Finally got around to turning some Christmas tree ornaments and that required hollowing through a half inch hole. Drilled the 1/2" hole almost through the shape I'd turned then used a dental tool as a scraper to get back up under the top. Had a round bone bur and a Foredom. So with the piece turning and the Foredom spinning the bur in the opposite direction the hollowing was easy - great for stuff to about
2 1/2" reach. That's perfect for ornaments. There are other ball type burs available if you don't have access to a bone bur.
So if you've got some sort of flex shaft and have avoided doing small hollowing - try this route.
charile b