I am thinking of making something with the glazed ceramic material, but would need parts that will fit inside other parts and such. The design rules say Pieces that fit together are suggested to have clearance of 4 mm (ie teapot & lid) but I am a little confused by that. For example: If I were to make some item in glazed ceramic with a hole in it say 30mm in diameter, what would be the largest diameter of item I could be guaranteed would fit in the hole? 26mm (4mm smaller in total) or 22mm (4mm total clearance between all sides) Does this 4mm rule apply to ceramic + ceramic parts only? If one of the parts was a made of a precisely cut material, what would be the minimum clearance then? It is also written that the glaze will add up to 1 mm of surface volume in some places. - Is this a guaranteed maximum?