Considering you've been using Elk Master, I'd leave it about 80-85% to begin so you learn what the tip plays like in a "pure" state. Cutting it in half may (and I did say may) be a bit much at first.
The old Moori's that were so great were firmer further down to help with shape consitency. Cut 'em shorter, start out firmer, get firmer faster - was the nature of the beast.
Don't know about the KB's. The tanning process they use is what makes them black, and also provides a lot of their positive attributes... Like holding chalk well, holding shape well, and being less effected by humidity. But I don't know if they are purposely made firmer as the layers go down.