Just my experience this year is do not do it unless you are committed, and your teachers are too. For me I did that this year in S6, identical to you with A at N5 Maths in S5 and no science in years. I crashed and burned because I did not put in the effort, and my teacher was not interested in helping either.
If you need it, and you have the willpower to catch up - go for it! But Higher Maths is hard, as is Higher Physics and sometimes you just need to pick one challenge.