Wow that is a small butt.
I am not sure if you have heard or read here, but smaller cuts of meat particular roasts tend to take a fair amount longer than the larger ones to cook. And since you don't want to brine, I think I would actually resort to using the "Texas-Crutch" on this one which I would NEVER do with a typical 7-10 lb sized butt. I just worry that with the expected extended cook time that it might take to get this one to temp and without brining it that it may want to dry out if you don't foil the butt after it gets to 150-160 degrees or so.
I would apply a mustard rub and your favorite low/no salt seasoning and go that route, smoke until the internal temp gets to the 150-160 internal temp range, and then double-wrap in foil with a little apple juice and take it the rest of the way to 190, then rest for a good 2-4 hours (still wrapped) in a cooler before pulling.
These are my initial thoughts. I will be curious to hear what the other guys/gals have to say.
