It's funny that you ask about my Methods background, Shannon, because it's quite unique. This is how my mathematics program fell into place throughout high school:
Year 7: Standard mathematics
Year 8: Accelerated (Year 9) mathematics
Year 9: Accelerated (Year 10) mathematics
Year 10: Mathematical Methods (CAS) 1/2
Year 11: Further Mathematics 3/4, Advanced General Mathematics 1/2
Year 12: Mathematical Methods (CAS) 3/4, Specialist Mathematics 3/4
So as you can see, I'm not studying Methods at all this year!
Also, my school did this weird supplement subject thing up until this year where the Methods students did a 'General Methods' subject in Year 11, but none of the accelerated students did it, so I am yet to study logs and exponents (I've heard this isn't too difficult though). Unfortunately I'm probably not the best person to comment on the matter because my school treats Methods as some special subject - no one is allowed to accelerate in it and you would probably not be allowed to pick it up at 3/4 without 1/2 at my school (my school is like this - I went through hell to convince them to let me do Biology 3/4 when most of the Year 12 course is different to the Year 11 course). I've heard Methods approximately stays the same throughout all Units with the exception of probability, which actually gets more simple.
If you really wanted my personal opinion, I think you could do it in Year 12 as long as you work hard and are willing to get yourself extra support (this might mean getting a tutor). I believe the actual course is quite big in terms of content and you will probably find it's one of your more demanding subjects. However, with that being said, Further will become a breeze for you and you'll probably be able to fill out certain modules of the exam without even attending a Further lesson! When people do six subjects in a year, you'll find that a lot choose one subject as their 'last priority' subject and merely aim for a 35 in it. Further suits this description perfectly for students undertaking other mathematics subjects.
It's certainly not the ideal situation, but I know exactly what you're going through because I'm going through it myself. If you want it bad enough, no inconvenience will ever stand in your way. My mum had to pick up Art in Year 12 and do two year's worth of work because she failed Year 11 Maths and it turned out to be her best subject in HSC. Whenever I'm feeling stressed about it all, I think of this. Hopefully it works for you too. Don't be put off by the challenge. 
Oh how I love and adore you.

So did you choose to do Bio for next year because it's a Uni pre-req or?
I think it's going to be difficult to convince the VCE co-ord to let me do 6 subjects in all honesty, hopefully I can persuade them well.
I was discussing the possible switch with my dad and we've agreed on me getting a tutor for Methods (hopefully someone from AN), I do see it for what it is, demanding, but it offers a challenge that my other subjects don't really have for me, since I chose subjects i'm good at and see it was a breeze to understand the concepts. Hopefully this allows for me to focus on it more, I only aim to achieve at least a 25 for methods, so it may be that 'last priority' subject, though it will be of my highest priority to get that 25, hopefully with improvement, I can achieve higher than my goal.
Wow! I was thinking about this earlier today, and in all honesty, AN is seriously such a valuable resource for me to have at a time like this, stories of people's struggles and success really motivates me, nobody in my family has passed year 12 in Australia before, so I didn't have anyone to turn to when I was questioning things, but to be able to talk to people who are in the same situation, and actually take time willingly to discuss with each other is amazing, I love this forum, I don't know if my recent AN addiction is getting to me, but I just feel so motivated right now!