at what age is a CsW fully grown??

[Mirkawolf]

The dog averagely grows up till the age of 12 months, after this, he will only gain a bit of weight and muscles.
Look on the pedigree of your dog. Look who is the mother, who is the father and their parents and look how high they were. That should give you hint about final size of your male dog. If the father and his father come from line, that was average or limited height (around 65-66 cm) and mother of your female was also on limit (60-61cm) then there is chance your male dog also won´t be too big.
Growing up also can be supported by the food (quality and amount), but the height is mostly given by the genetics. In the age of 11-12 months do not expect any big changes.