Well from my experience with damsels, I wouldn't go with the four stripe. They tend to be very aggresive and territorial, same goes with your clown fish for that matter. The yellow tail is a fairly good choice, but those can also get aggresive especially in a 29. With that small of space, you will have a lot of fighting going on. Stick with the royal gramma, and maybe try an ocelleris or common percula (sp?) clown fish. Also I really like my orchid dottyback, not the purple dottyback. Maybe a sixline wrasse would be good too. You really will want to limit yourself to three or four small fish over a period of time.
Of course when getting the new fish allow at least a month or two between adding new fish, so as not to overload the tank. I hope this helps.