Overengined
commented
1 year ago Slug and Pound Force wouldn't make a lot of sense in my opinion because they all got replaced officially by a standardised metric equivalent. However, psi is still used on a lot of pressure gauges around the world, so I guess it would be interesting to add it for practicality because because of its wide usage.
The foot, pound, second units of measure missing from the available options are as follows, The pound force (lbf) defined as a pound times the standard gravity or exactly 4.4482216152605 N. The slug (slug) defined as lbf s^2 ft^-1 or exactly 8896443230521/609600000000 kg. The pound per square inch (psi) defined as lbf in^-2 or exactly 8896443230521/1290320000 Pa. While they may be somewhat obscure, they are still very much in use so I hope it wouldn't be too much of a bother to add them to the list.