Welcome to the EGGhead Forum - a great place to visit and packed with tips and EGGspert advice! You can also join the conversation and get more information and amazing recipes by following Big Green Egg at:
I bought into the spatchcock hype for a a while, and still cook that way sometimes. I agree that it does nothing for the chicken retaining moisture. However, cooking a chicken upright allows fat and juices to run out the bottom of the bird. When you cook lying down, the fat and juices gather behind the skin and the skin is soggy unless you let it dry for quite a while...usually overnight. Tonight, I cleaned a chicken, patted dry and put in the fridge for 30 minutes to help dry. Skin was like potato chips and the met was juicy and tender. Im back to cooking chicken on my beer can roaster setup. I just get more consistent results....and i can fit more chickens upright than i can lying down.