Having worked as a tipped server, I also would like to add that it emphatically does not improve the overall level of service that a customers will receive. Simply looking at the incentive structure you have built it should be obvious where there will be problems. It is basically a sales position where you are paid on commission, and that's how all servers who have been in the business long enough look at it. Imagine, for the sake of simplicity, I have a two table section. One table has a party of six and they all order drinks, starters and expensive entrees. The other table gets waters only and shares an entree. Who do you think will get my attention as a server? Now, if this were a real scenario most servers could handle two tables like this no problem, but if it were an equivalent scenario where the server's section was at capacity, it's going to be the two-person party that gets the minimum amount of service to make sure I don't get fired, and I will do everything to make the six-person party happy. If you give me a shit tip on a 20 dollar check, I do not really mind, especially when this other table has already spent 200 dollars and are asking me about dessert and after-dinner drinks. The two-top will get their water refills when I am sure the six-top is satisfied with the expensive wine they ordered.