Tom,
From what I can tell, every smoker seems a little different. I was able to reach 260+ with 4 racks of baby backs, whereas your smoker seems to hold lower temps. No harm, no foul. My single rack of baby backs turned out perfect tonight at 235 for about 4.75 hours. I made a different rub and put more on. I'm not sure if this creates more bark but the results were spectacular. Definitely what I was hoping for when I bought my SI2. Now that I made a good batch of baby backs, I may try a Pork Butt next.
I remembered to take pictures this time. Haha.