Welcome Kevin:
With your talent with stone, tooling leather should be very easy. I would recommend "Figure Carving Finesse" and "Pictorial Carving Finesse" by A. Stohlman, in my opinion these are the bibles of that that aspect of leather work. You are correct the labor involved is not conducive to what the market will bear but the love of the craft makes up for it. At least that is what I keep telling myself. Welcome to Leatherworker.net, again in my opinion, the best leather working site on the internet, where you will meet some of the best people in the world. I have tooled leather for 30 years and thought I knew a thing or two but after finding this site I quickly realized an old dog can learn new tricks. Everyone has been great offer suggestions, tips which would have costs several dollars to buy the book.
I will get off my soap box and let you decide for yourself, but again welcome and look forward to seeing more of your projects. The saddle bags are fantastic.