Yeah, I think the best thing to do (bit late now) is ask some teachers who have marked creative at the marking centers (or any module at the centers, they all discuss things). Ask them how many of the top responses look planned. Generally I find they say that most of them are really good stories, with good integration (ie, they have planned them). I guess it really depends how fast people can think on their feet. Also it varies each year, some years the question will be designed so that you cannot go in with a prepared response, the BOS recognises this (from the 2009 Marking Center notes):They were generic, though I had to do some thinking. I hate stimuli because I incorporate it, but I don't know how much they expect of it in terms how much to incorporate.
I agree with you regarding the superficiality of the stimuli.I did not find the questions easy at all though they weren't nasty, for Romanticism, i did not include much textual form manipulation and literally, i hate to say this, bullshitted through my essay. But I'm glad it is over. The creative was alright but like you guys said, I am now uncertain at how they are going to mark it, I really just regurgitated my story and reckon I included the stimulus in a superficial sort of way.