BHT - thanks, you may well be right, though as you say this is less of an issue for me. I am more interested in doing different things, though I would also like them appreciated!
Since I commented on the potential re-usability of the central leftover with this method see the attached, all made from the one original piece. The middle 'bowl' is made exactly like the first (ie from the central leftover cylinder from the largest bowl) but the smallest one is cut and hollowed from one side (though also from the central leftover from the middle bowl). It is OK but less neat inside than the other two.