RAM is RAM, no forcing of details is necessary. I agree with pressing F12 though, simply to make sure you have loaded the correct RAM (although as long as you replace the original it shouldn't be a problem!)
Maybe force is the wrong word, but I can only get the emulator to use a different ram file by actually hitting f12 after the substituting and renaming. Maybe it is because I only move the original. I was just always advised to use f12 after I once queried why replacing the ram hadn't worked.
bj