Question about skeleton mesh combine

Hi guys,
I have two question about the skeleton mesh combine.

  1. In my game I have a lot of low poly characters, and each character has 14 modular parts. So when I render like 30 of them, the performance is really bad with fps to 20. If I change the low poly characters to be single skeleton mesh(no more modular parts), I could do like 100. I used the profiler it showed that using modular characters the shadow and drawing takes really longer than none-modular.
    So I am guessing I need to a runtime combine modular parts into one skeleton mesh when loading the game right?

  2. Another question is that, when I changed some of the character’s equipment, all the modulars parts are already merged into one skeleton mesh, what should I do then? Like I change the Torso part with a new mesh, should I do a combine using the merged one skeleton with this Torso part only?