Trying to describe how the stone changes was difficult, and admittedly, reading back, I can see where the problem is; and I'll have to update the vertebrae count to lessen that, because looking back again, jebus, he would be stiff as a board.
Here's a quick reference of his stone's aging scale for visual reference; this hopefully clears things up, and I can add it into his profile no problem. Describing it, it seems like it changes drastically and grows to enormous size but this is what I was intending to get across;



Bearing in mind that much of his stone is under the skin, encasing and replacing about 6 vertebrae's length. I'll go about updating his profile to reflect this as well momentarily, but I wanted to clear things up and get the okay for this design now that there's a visual reference (albeit not finished being colored lol) for his stone's placement.
Full body btw;