Yep, I realise this (and you have inferred correctly that I intend to serve the built object as an http response), but that doesn't answer my question.

I'll be able to print the header okay, it's the binary data which forms the built swf object that I can't see how to get hold of (other than saving it to disk with a temp name, reading it, printing the contents in the response and then deleting the file, ug!)