The 2mm works very well in the Killer, (don't have a Penny... yet). I use two strands, or one doubled over. Torch the Ekowool with a chef's torch or hot butane lighter before you cut it, it will help keep it from fraying. That's about the only downside to it, the fraying, but it actually helps promote wicking.
Be careful handling it after you torch it, it stays very hot for several seconds.
Jack
Be careful handling it after you torch it, it stays very hot for several seconds.
Jack
I need a sticky pad. 
