I have not turned a platter before, but I have turned a fair bit of kiln dry wood. Before I knew about the joys of green wood turning, I used to go to my local lumberyard and buy cutoffs of their 8/4 stock and turn bowls and small hollow forms. Lots of dust and harder to turn than green wood, but it was stable and I got good results. I would not hesitate to use kil dry wood for a platter - in fact, it may be more desirable than green wood!
Man advances just in proportion that he mingles thought with his labor. - Ingersoll