For the best info you should definitely speak with the class action lawyers and have a chat with your own lawyer too, but:
Typically, class action law suits are designed to prevent individuals from seaking their own suit. This makes sense as there's no point in having thousands of seperate law suits, all arguing the same facts. So the judge typically designates one suit as 'the' class action.
I think in this case you're either all in or all out. But without seeing the actual text/documents you got its difficult to say, so the above is merely a general rule. Also, if you have other facts or charges than the class action you 'may' be able to use your own lawer. Mind you, good lawyers are expensive! dividing the costs amongst the shareholders is the most effective way to recover losses from Sino and related parties.