Agree about not putting too many fish in, one of the reasons TheConches tank is such a beauty is that he has not overstocked it.
It is a very common mistake for people starting to put too many fish in it is so tempting. Plus, people are often used to FW stocking levels, but the fishload capacity of a SW tank is much lower.
I don't have a RSM myself so cannot speak with experience, but i think 2 very small juvenile occellaris clownfish would be OK. These kind of fish don't have much territory in the wild and can be totally happy in a tank this size. They also don't eat as much as other fish the same size thereby reducing bioload, and will also stay small in a small tank. But if TheConch has a different opinion on that i will bow to what he has to say.
Also, clowns would be much happier, plus more interesting, if in an anemone, they would be completely as in nature. Still waiting for TheConch to see how an anemone will go in a RSM, any progress on this Conch?
Alternatively, just a small flame angel, as TheConch has, is a happy option the flame angel is one of the most awesome coloured fish and adds much beauty to the tank. My suspicion is it will outgrow the tank in time, but if this happens it could be sold and a new one purchased.
What Markoshark said also, in a tank that size a damsel will have a tendency to badger other fish to death.