Idk if I'll be of much help since I'm currently doing Chem1031 this semester, and I've only done the midsem exam which both chem1011 and chem1031 did together. If you got a band 5 in hsc chem then I'd do it. I'm finding the content so far pretty decent and I also got a band 5. I compared the content with friends doing chem1011 and theres a bit of extra work in the lectures and in our lab pracs but the level of difficulty isnt that great. That being said, I've heard the exams are alot harder but it scales well.