I am planning on smoking 2 on-the-bones prime rib roasts for Christmas dinner. These are the big 7-bone roasts, about 17" long and 18.4# & 20.2#. I have done several of the smaller 3-bome roasts before, and am wondering if these bigger one will take much longer. Smoking in a FEC100, and will be following Smokin's Prime Rib tutorial. MY thoughts are these will take about same time as would a smaller 3-bome roast since the diameter of both roasts are similar in size. I would not think the length of roast would have that much affect on time needed, but hey - what do I know ??!!??