The rims and heads are not in different groups. They can be set to be in different mute groups so that when you strike one, it mutes the other. With the dual zone feature, there are setting for zonextalk. This is the xtalk setting between zones - bell/bow of a ride, or rim/head of a tom/snare.
From what I can tell of my toms/snare, there is one piezo on a strike/reflection plate at the top and another piezo mounted at the bottom (both are in the center relative to the sides).
I'm not 100% sure about the mute functionality - I'm not sure if I've ever hit a rim and head at the same time. I may have... if it muted and I didn't realize I hit both, then I would know anyway!
I would try what you already have to see if it works before changing it up. As I stated before, you can always tape the leads to a TRS cable to try it out... just hit the head and rim fairly lightly... as to avoid a disconnect.
I hope this helps you.