I wish I stuck with further for 1/2 in yr 11. It was an extremely unwise choice picking methods up for the unit 2 part. It also sucks that I was placed in that situation because the school messed up my subject selection.
Story time: So I had to do further unit 1, while studying myself on methods unit 1 at the same time and do both the exams (I need to score high in both as well). I then was placed in methods unit 2 and just barely passed the SACs (except one where I got ~65%). I then bombed my exams (I failed both of them).
End result: My stress levels reached an all-time high, I have never cried more in my entire life, I was left in a dark mental place, a toxic mindset around teachers, maths and my school.