On both my Big Bangs (Black Magic and SS), I just removed all the screws and then the casebacks came off.
On the SS, it was very difficult at first, but with a little effort and a small screwdriver inserted, I would wiggle a little, move around the case a bit, pry underneath again, go slowly and it eventually popped off.
On the SS, it was very difficult at first, but with a little effort and a small screwdriver inserted, I would wiggle a little, move around the case a bit, pry underneath again, go slowly and it eventually popped off.