Doing well depends on many things. But just remember your assessment mark is only 50% of your HSC mark.
Your rank is vital. Even if you have a pretty crappy raw mark but a good rank you should still do ok provided that you and the majority of your form performs well in the HSC exam as it is the collective performance of the form in the HSC exam which determines scaling.
If you have a failing raw assessment mark I don't think 40-44 is out of the question but you will have to do fairly well in the exam.
Last year I had a raw mark of 33/50 and a rank of 11/45. I got 57% in my trial exam. My results from the board were as follows: assessment mark 45/50, exam mark 46/60, HSC mark 46/60 E4. A couple of people in the top 10 ended up below an HSC mark of 45/50. So you can see that a lot rides on the final exam and leapfrogging a few people is definitely possible. Don't sacrifice 3u, it's a good subject to have for your UAI.
Hope this helps.