I do flats all the time and they turn out awesome. I pick up them up at Costco, 4-8 lbs, USDA choice grade. I did a 4.7 lb flat last weekend put it on @10:30 am, foiled at 170' 3pm. Pulled @ 205, at 5 pm, let it rest until 6 pm and it was perfect!
Forgot to say I am running at 225-230 degrees