I have a friend doing maths, further maths, chemistry, physics and an EPQ at A2 but he's doing most of the EPQ over summer. It honestly depends on how easy you find maths/further maths, because if you only spend as much time on them as you would on a single maths A2 and manage decent grades, you'd probably be fine.
At the end of the day you can always start with those and drop one if it's too much work.