Silkies in this country are Bantams. According to the American Silkie Bantam Club, the birds should weigh as follows:

Feather Legged Bantams –
Weights: Cock 36 oz. Cockerel 32 oz.
Hen 32 oz. Pullet 28 oz.

Check out the SOP for the breed here:

http://www.americansilkiebantamclub.org/standard.asp