Is there a formula (or rule of thumb) for predicting mouth feel/body or is it a trial and error thing? I've brewed a couple of batches already and would like to try to make my first extract recipe. I want a stout, so I'd like a way to create a heavy bodied beer. I've heard that you should add malto dextrin for a heavier body, but never really how much should be added. Any suggested reading? And yes I've already read "How to brew" by John Palmer.