Based on the fact that you said it is required as a pre-requisite,
yes totally take on methods 3/4. Personally I found it a very rewarding subject. I completed spesh alongside methods this year, so I understand where you're coming from when you say it was on the backburner, however I would be hesitant to say that having free periods will help your situation. You may not be as productive as you hope, and especially if you aren't the strongest math student, in class time is golden. Additionally for most cases, 6 subjects in total is a great situation, and 5 in year 12 (unless you've completed 2 this year) gives you the option to drop a subject if you think you can't stand it
or if you fail but yeah i don't believe that will happen since you're seeking advice therefore i will assume that you care for your education If you believe that you can commit to the subject, do it. Methods was tied with psychology for my favourite subject of the year. The concepts studied all link together as compared to the other maths studies, so it's nice if like myself you need a holistic understanding.
If I may ask, what is your desired career goal? Keep that in mind throughout the year as you complete your studies and it acts as great motivation xx I honestly believe that if you can put the effort in that you will be an amazing methods student and I wish you the best of luck for 2017 and onwards regardless of your decision xxx