Declining is a tricky one. I hate to decline anything, because I slip down in the searches when I do. But rather more often than I want to I have to decline, and it is ALWAYS because they have read, but ignored my rules. Message will go like this:
''I know you say that xxxxxxxxx is not possible, but would you do it just for us, just this time? We really want to stay.''
Repeat ten times. I even say in my writing ''please don't ask me for xxxxxx, as I don't want to decline your request.'' I change this wording regularly, trying to hit the right words but haven't yet.
Since I don't have IB, I don't have to cancel anyone and you must NEVER do that, definitely will be a penalty.