The only real problem with study timetables is the burnout in the end. The motivation from when you create your timetable to when you sit your HSC exams progressively decrease, which makes sticking to your study schedule all the more harder. I mean, props to you if you're able to maintain it throughout the rest of your HSC journey, but unless you're really organised, you'll slowly find yourself slipping away (due to external factors).
So, when you're writing up a study timetable, consider study strategies that work best for you in terms of content.
For example, preparing for English isn't just writing essays under exam conditions, or rote learning your creative; that'll only get you a b5, at best. Instead, use some of your study periods to dive deeper in your research. Module A asks us to compare the contexts and values of two texts; we're asked to appreciate the texts, both as a whole text and through the writer's perspectives. So, take some time to hone in on the depth of each text, why and how each composer uses their medium to convey their message. Look for macro and micro techniques to embellish your analysis.
For mathematics, past papers can work, but also take the time to master the concepts. For extension 1, it should be second nature to you when asked to derive the six equations of motion, as well as finding the max height and horizontal range. Once you master your basic concepts, past papers are the way to go; sit them under exam conditions, or glimpse through the paper to find specific questions you won't be able to do. If these questions follow a trend, find your weakness and use your study periods on your timetable to hone in on those topics; it's a lot more effective that way.