Adding hole close to top of barrel

I am new to this forum, and had a question.  i am in the process of building a UDS and saw on online, the pit master i believe it was called that had two hole close to the top for hanging, has anyone ever done this with the standard UDS.   By standard i am referring the design where you use 3/4 ball valve to regulate air and have the other ports for starting.  does anyone know if this would affect the heat, would i still need a top vent or stack...any ideas or suggestion would be appreciated.