My experience has always been to go to the top with your "up front" tip. For example, my wife and I both love shrimp coctail as an apetizer and would love to have it each dinner. On the first evening I ask to see the head waiter or matr'd. Slip them a few bills and tell them of my request. Like magic, shrimp coctail appears each dinner. As an added benefit the person tipped shows up at our table each evening to make sure "everything is ok" and to find out if there is anything else we need. Each additional request is of course acompanied by another tip. Works every time, and by the way the word gets down the line to the waiter and bussboy of our generosity.
Regardless of what happens to or where you last day tips go, up front tips ensure not only good service but special attention. Flame me if you whish but I want to be pampered and catered to on my cruise.