I had the same problem, and I did this a couple of years ago, and it worked great.
I actually fragged mine into 3. I used a dremel to cut into the skeleton at the back - there were natural spots where it was slightly less thick, so I used those. Then I used a chisel in those cuts to gently break the skeleton - the goal is to break the skeleton, but not tear all the flesh (I had some tearing, but not too bad). I did a dip in tank water dosed with iodine, then into the tank in a low-flow area. I put a wedge in each split (I used broken bamboo skewers) so that the flesh would pull at the break.
Over a couple of weeks, I would expand the wedge and gradually get the flesh to pull/grow apart until I had 3 bubbles. Actually, I am overdue to split it again - it killed some duncans recently as it is getting too big again.
Good luck!