We have one domestic flight scheduled on China Southern on our upcoming trip in March, but are a little dismayed at their baggage allowances. Their website says if we're flying economy, then each passenger is allowed 20kg for checked bags and 5 kg for carry-ons. Do they really enforce that, especially for the carry-ons? Both seem excessively restrictive and not at all in line with the other carriers.

Assuming they do enforce, anybody have any idea what excess baggage fees may be?

Thanks for your help!