Correct Visa for Postdoctoral Research

I have been awarded an Endeavour Research Fellowship by the Australian government to undertake postdoctoral research for six months in Beijing. My Chinese host organization will be a private company, not a university. Should I apply for an F or for an X for this visit?

Also, which is best and/or easiest, in terms of types and their requirements: to propose a stay of just 180 days, or one that lasts the full six months (182 days)? I see that it might make some difference to the category and the corresponding residence permit, but I can't tell what the advantages are, if any, of staying either more or less than 180 days.