Just finished mine. I had the same issue with the ring. It was too tight to fit in as one piece but easily snapped into 3 pieces at the dividing lines and I was able to fit it that way. It was still tight. to fit the inside piece into the outside shell I had to shave the lip that connects them and push with some force. I did .16mm layer height and my machine is pretty well calibrated. Came out great as a finished product.