Pat, Two points: *On 2 L drink bottles, this is factually incorrect. Statement of the required contents in Customary was required since 1966 under FPLA (before the 2 L bottle was introduced). Supplemental metric was allowed until 1994, when its addition was required. At the moment, omitting either is illegal. Wine and spirits are a bit different. Both the size and metric declaration are mandatory. Customary is permitted in addition. However, the 2 L bottle is a good example where the public thinks 2 L and not the cumbersome 2 QT 3.6 FL OZ (67.6 FL OZ) which is also legally required.
*If you have Excel, you have an excellent double precision floating point resource, although you have to fuss with formatting to display all that precision. I use an HP15C calculator, and when 10 digits isn't enough, I also use a virtual RPN calculator on the web which uses double precision floating point. If we ever get more converted, I don't want people saving the inch to define the gallon. We can push all Customary units to completely rigorous metric definitions. Whether that really helps is debatable, but I don't see how it can hurt. Intermediate Customary definitions are not required and needn't be preserved (like 231 in³/gallon). ________________________________ Consider the upgrade to two litre drink bottles. A decision was made to use this size within the management structure of one of the drink companies (possibly because they could buy cheap moulding machines on the world market). No attempt was made to provide customary equivalents using "metric conversion" and none proved to be necessary. The public soon bought drinks in these bottles, got used to the two litre size, and then - in a few days - got on with their lives.
