As usual, I'm going to offer an alternative opinion.
I don't worry about 300-plus temps during the first 4 hours. I didn't have any problems with the two butts that I've done where the INITIAL temps were that high. In fact, the temp was that high for much of the first 4 hours (I was using a Weber kettle).
I think that where you might have to worry about it during the last half of the process. I think that since most of the meat is "cool" and mostly uncooked in the first half of cooking, that higher temps aren't all that much of a problem when it comes to potentially overcooking the butt. That's a large thick piece of meat to have higher temps overcook it (in the beginning, at least). And I never had a problem with the outside of the butt being tough and overcooked.
I realize that your smoker is different than the Weber. However, until the internal meat temp gets to around 150, I don't think you have much to worry about. Of course, once it hits that time/internal temp point, temperature becomes more mission-critical.
Just my observation based on my limited experience.