I live in Shanghai and fly CE a lot, points usually post fine. Check out the website of China Eastern and try to book directly via them, you can add your Flying Blue number in the booking and quite often you can get much cheaper rates not available on international sites such as Expedia, especially for domestic flights in China. Another benefit is that you can see the actual booking class your booking (L, M, N etc.). link: en.ceair.com.

An alternative is Chinese travel agent Ctrip - they actually have the option to, on quite a few flights - not all - select from multiple booking classes. During the booking process you can choose the actual booking class. It won't show the 'letter' of the booking class but it will warn you if it is a non-mileage accruing booking class. They have a very good online 'chat' function on their site, so if you need to know the actual booking class it'll take you two seconds to ask without having to phone them. link: english.ctrip.com

Cheers
Matt