Thanks everyone, it looks like carving first is the way to go. At this stage I don't intend to do any border stamping, although that may change, my thinking is that "simpler is better", with just a grooved edge around the carving. My first issue is to try and master the principles of Sheridan-style patterns. I have the template made up for the holster size now I have to design a pattern to fit (I didn't like my first attempt, it just didn't look right).
Going to be a slow job!