We decided to make two hams for this Christmas for the family party. The question, however, is whether two hams should be cooked at the times suggested for each, based on weight, or whether to add a certain amount of time or even double the time.
A search of the internet found several opinions, all of which advised that the cooking time should be based on the size of each ham, not the two added together. So, if it's two 8 pound hams, then the time should be based on 8 pounds. One suggestion said that ovens without a fan (convection) or that is filled up with the two hams will take longer. I also read that if the hams are different sizes, just start the bigger one first.
As far as how much longer to give the hams, that's the part that will probably be different for each situation. We're planning on an extra 20 minutes, just in case. We'll see how it works, but we'll also just keep an eye on temperature and turn the oven down if both get done before we're ready to eat.