Yes they can spike the temp, but it's something you have to manage, most fellas that are good at running offsets run the smallest fire that will maintain temps and they run the fire hot with good airflow, they manage temps by the size of the fire as much as by airflow. You sound like you want to run charcoal as your fuel and chunks, so yes you will get spikes but don't worry, let them temp run up a bit, it will settle down, don't sweat temps going from 250 up to 275 or even higher, it's all good, let it ride. I'll run my cookers anywhere from 225 up to 325 and I'm good with that, chicken I'll run even hotter. You don't need to hold one set temp the whole time.