Mountainman,
No, twelve inches is not too small. You will need it all. I think I cut a stock out of wild cherry from a fencerow that was maybe ten inches. But you will get only one stock from it. You may get two or three out of your twelve inches if you cut very carefully.
Now, other opinions will differ, but do what you can with what you have. All that you will loose is log.
volatpluvia