I make and sell barrel type smokers and do believe you'd be better off using a 85gallon sized cooker to start with. My units are high airflow or convection type smokers, so cook times are not slowed down by big loads to the degree of a standard design. Eight on a 55gallon , with standard airflow(pipe nipples) would cause a concern of time delay and uneven cooking. Just bump up to the next size and you'll be able to cook as you want. When using my racks, thirty racks of spares can be done at once on a 85gallon model. It comes with three grates to use.So cooking eight butts at once is no problem. Good luck. Steve.