Eyebuster,
I've done two 6lb butts @ 215 degrees in my SM025 (one on each rack) and it took about twenty hours. The final product was fantastic and I received many compliments. I trust Tom's comment that the "smoker cooks better full" and maybe this will shorten the smoke time. Just remember what SmokinOkie always says.."it's done when it's done". Be patient and when you hit the target temperature you won't be disappointed.
Good Luck!