Do I need to use the same thread in the bobbin as the top?
No. In fact, I will not run 12 wt both in the top and bobbin. It is simply too much thread to fit through the clearances around the shuttle. The rest of the Sulky lineup of threads can be exactly matched, but many times I will choose a finer weight of the same thread because more of it fits on the bobbin. I prefer 40 wt. Rayon or Poly Deco in the bobbin when running Holoshimmer, Sliver, or Metallic in the top.