I like the rear drum, stone ax simple and nothing to leak. I would never convert to a disc but might very well go the opposite way, disc to drum. I also like a 16" rear on the Specials. I think it looks better. It was designed for it, the way the side covers angle down towards it.
One of the 1st things I did when I got my Special was swap an 18" rear onto it because I read they handle better. I didn't find that to be true. It handles just fine with the 16" and is actually better in a straight line at higher speeds with it. So, I switched back and will be staying with the 16".