i just got off the phone to an english teacher on the HSC helpline who was so awesome. Helped me soooo much- one of the questions i asked her was if i should prepare two Supp texts or just one. She told me it was alright to use two, unless the question specifies to use more than one- then just one will be fine as well. I asked because one of my Supp texts is a painting and unless you're brilliant (which im not), you can draw so many journey links from it by simply looking at composition and style of it and get really good marks. And normally, the links are all assumptions and in my opinion, it doesnt sound right. So if you do just do ONE when it says "at least one" in the question, you wont get marked down for doing that (unless all the texts are not of a different medium/mode of production).
She also said that if you pick a text that the markers will not be familiar with, normally- you have to give one or two lines describing the plot, etc so that the marker has a slight idea of what its about. And if you can pull it off by making some really great links to the concept of journey and answer the question in depth, than by all means do it. Im doing Donnie Darko, and most people i know have no idea what is about so i assumed no1 knew. But the teachers/hsc markers ive talked to have, so you never know who knows what.
If you're still confused, call the helpline- totally recommended because the last few times ive called, i always get the awesome teachers. Just, dnt call at the last min tommorow because- im sure the lines will be clogged.