Just curious, why a little ring-light?
Ring-lights produce flat results, flat as a pancake.
Big Ring-light strobes produce a shadowless effect often used for fashion, but for macro I’ve never understood the concept of dead-on flat light (except maybe for scientific recording where art, or modeling the shape of the subject, isn’t the objective.)
Here’s an alternative to consider:
Add an extension arm, get any two small speed-lights to mount on the arms,
and get a double split Y sync cord that plugs into the S2’s sync port:
http://www.paramountcords.com/Ycords.asp
Way more creative control of the lighting effects.
-Marc