the weight units under the grouping of Chinese imperial is not really Chinese imperial. They are the modern version of the Chinese imperial. Otherwise, how can 1 Chinese imperial tael exactly equals 50 grams, and 1 imperial catty exactly 10 teal and half a kg?
In other words, the names used in Mainland China now are old units' names, but the actual weight they refer to are nothing but imperial. The actual weight they refer to essentially is metric (i.e. 1 kg = 2 catty)
Patrick