Jake,
It's not the out of round issue that is causing the temperature spikes. It's the design. It's made with air gaps. Fortunately, I've found that most of the foods that need to be rotis'd like chicken cook better at higher heat.
Ribs, incidentally, are INSANELY good on the rotisserie at higher heats. They aren't as tender as low and slow, but they are much more flavorful and with a crispy crust, and they only take a little over an hour to cook.
Having said all that, if you want to keep the temps down, you can do it by stuffing foil in the gaps between the gaps between the bottom of the ring and the base of your kettle.