I am a hobby builder, not quite a gun a year. I use aqua fortis on stocks and on other projects, walking sticks and canes, so my experience is not nearly as rich as others. I have used it on Maple, sugar and red, Ash, Hickory, Walnut and "Japanese Cherry"(that is what Dixie claims it was). I am happy with the results but have come to the conclusion that for me, to misquote the great philosopher Forrest Gump, Aqua Fortis is like a box of Chocolates.
My theory, and I reserve the right to be wrong, is that there are three variables, the regent, the wood and the heat. At the present I'm thinking the wood and the amount of heat produce the greater variation. I'm thinking anyone with the knowledge to write a comprehensive work on the use of Aqua Fortis wood have a best seller in our little community.