No unfortunately you can't
I did the HSC with 13 units and I regret it as one whole subject I worked really hard for and expected to count didn't and my lowest mark counted instead which I was not prepared for because I didn't have enough time and it WAS one of my better subjects. My advice is 11/12 units, thinking about it in my case one unit can make a big difference, if I could do it again I would have done 11 units. Dropping extension history I think is a good idea, as it is a lot of work. Keep ancient for the moment, if you find it gets too much (come trials) DROP IT
Hope I helped...
I did the HSC with 13 units and I regret it as one whole subject I worked really hard for and expected to count didn't and my lowest mark counted instead which I was not prepared for because I didn't have enough time and it WAS one of my better subjects. My advice is 11/12 units, thinking about it in my case one unit can make a big difference, if I could do it again I would have done 11 units. Dropping extension history I think is a good idea, as it is a lot of work. Keep ancient for the moment, if you find it gets too much (come trials) DROP IT
Hope I helped...