Thanks all. I think it's pretty much stopped moving now, I don't expect any real cracks, the rim is very thin and the bowl is pretty thin with just a bit extra in the base (bottom quarter) to help resist too much warping of the bowl area. Keeping the bowl as round as possible also helps with this. They only really crack on the outside bottom of the bowl and even then only a little which is easily stabilised with CA & filler. It's been a fascinating journey playing with such warpy green wood, I've learned a lot and am really looking forward to trying out similar techniques on some of the piles stacked outside.....