So if you use element MP1 your sed calls would look like this ofr Metric - actually you can use only one such file and add the mph here itself and use the same file for both metric and imperial - what say ???

sed -e 's/Calm km\/h'/'\$\{offset 8\}Calm/g' |
sed -e 's/Calm mph'/'\$\{offset 8\}Calm/g' |
sed -e 's/New'/'\$\{offset -13\}New Moon/g' |
sed -e 's/First'/'\$\{offset -5\}First Qtr/g' |
sed -e 's/Full'/'\$\{offset 6\}Full Moon/g' |
sed -e 's/Last'/'\$\{offset -5\}Last Qtr/g'
See if this works