I go the other way. I cook fat side down, and when it goes into the foil, fat cap up. IMO once it's in the foil, all the moisture is trapped inside the foil so if the bark is going to get soft it's going to happen no matter which way you do it, cap up or down. I never had any problems with the bark doing it this way. Yes if you foil a brisket the bark will be softer than non foiling, but it's a good way to get those great results, moist and tender.