I bought an 8″ and then adapted the 6″ lazer bit from my hand auger to it. It works mas bueno, and rips through ice at about 4 seconds/foot. The adapter was made from junk excess from the hardware store and took about an hour to put together. I’ll try to get a picture today when I’m out.
The nice thing is that I have the 8″ if I ever need it.