Mr.james, you can apply for a single-entry L visa (Tourist Visa) and ask for 6 months stay duration, Normally the duration of stay of a "L" visa is 30 days, which means the holder of the visa may stay in China for up to 30 days from the date of entry. If your estimated stay in China is longer than 30 days, please make it clear in the application form and ask for the Visa Officer's approval when you submit your application..

maybe your 6 months stay duration is refused, you only get a single-entry visa permits 30 days stay duration, after arrival, you can go to the local Exit & Enter Department to apply for extension of stay duration, however, the L visa can only be extended twice.

you can also have a try to apply for double-entry visa valid for 6 months, you ask for 60 days stay duration per entry.

Consular officers decide on the visa's period of validity, duration of stay and number of entry in the light of China's laws and regulations.