I had the km-6(black one), tuned to drop B, then finally to D. I went through no lie like 7 string gauges and the thing wouldn't hold tuning. Had nut pro filed, etc, still couldn't get it. Loved the guitar, pickups ruled, but I traded it locally for the km-7 mkII. Glad I did.
At first I wasn't sure I wanted the 7 string, but the mkii's have a 5 piece neck and the Ernie ball compensated nut, even on the 6 string model. The first series km-6's(black and white ones) had a three piece, and being so thin, I could tell couldn't hold the tension. Maybe I had a dud? But the mkII 7 I have now is awesome. Holds tuning, and has a really alive sound.
I want a km6 again and am hoping Keith has a new model this upcoming year, cuz I didn't wanna have the 6 and 7 the same color...cuz both mkII are that natural flame color. Hoping it's mkII specs with different color options.