Possible gotchas of embedded FlashPlayer?

Question

I'm using embedded FlashPlayer in windows forms application. I'd like execute action script functions from C# passing unicode strings as arguments.

According to adobe to invoke actions script function one should call CallFunction with a string that contains xml request. But they didn't say anything about character encoding of the xml request (I need to pass utf8 characters). I'm a bit worried as the function invocation fails if the xml is indented which suggest that it is parsed manually.

Questions:

1. Is safe to pass utf8 characters as parameters to functions calls?
2. How long can be the request parameter for CallFunction?
3. I'd like to hear about any better way to invoke AS functions from C# app.
4. Do you see any other potential problems with such usage of Flash Player?