Hey Psy..
I've been working with my '18 for awhile now, and I've discovered the "sweet spot" seems to be in chopping with the draw knife, in short chops, instead of using the hatchet on the end. If you get a chance, try that out, let me know if it works for you. I was destroying 5-6" cedars with this method with about 10 chops. Never tried a 2X4 though..