Cooking Times?

So Im looking at cooking for some friends this Sunday but I need to double the amount I would normally cook and Im not sure if I need to adjust the cooking time. Here is what Im looking at.

I normally cook 5lb of pork butt cut into 1-2 inch squares at 350 for 4hrs. But Im looking at cooking 10lb, should I just stick with the 4hrs or increase the cooking time and by how much?