I realize this is an old thread but I thought I'd share what I did. I have a couple phatties and I love them but there was one that was awkward in shape that left a smaller awkward area nearby. I tried to split it from the base out and it was clear that wasn't going to be possible but I did get about 3" out. I was separating a small section off (maybe a cm). So I cut it at the farthest point out. I was careful to cut it off the main dread in a way that it left a smooth area in the larger dread. Then I took the little newbie and gave it a wool extension that I just braided on and placed a wool bead where the real dread ends. It's not ideal but it feels better and the little guy will get congoed with new loose hair
I wouldn't ever recommend doing it, unless it was causing a problem. And this one seemed destined to be one. :P