444-4221C. Those are the ones I'm using on my IS. No complaints whatsoever, even two-up on Austone tires.

With 2up do you notice any additional scraping in normal curves/turning? I did with the 13" Progressives and the Avid Envigor 205/60-16, which is about 1" less diameter than the Dunlop MTs. Right now I'm riding on the Progressive 14" Air Shocks to add back that 1". With 2up I can lean over far and don't scrape anymore.
I did some scraping in corners when two-up with the peg lowering kit. Didn't need the peg lowers so I took 'em off. We used to bottom regularly on 416 air shocks that came on my Tourer, but they were needing a rebuild and I didn't want to mess with that. I have 444s on both bikes.