I am fairly new to this too (only been BBQ'ing for a little less than 2 years). Initially, when I decided to take the plunge and branch out to brisket, I tried several flats, albeit none as small as the one you tried for your first attempt. My results were hit or miss during my learning process. Some were very good and others got fed to the dogs. Now, I only cook 12+ lb. packers and the results have been consistently very good. I think there is just a much bigger margin for error with a larger piece of meat.
22" OTG; 22" Performer; mini-WSM; Brinkmann gasser; UDS (on the way); Maverick ET-732