I finally decided on prime rib. My question is about timing. It's a 6# prime rib and I plan to smoke it at 275 degrees. So that I have a rough idea about when to put it on, can anyone give me a ballpark idea about how long to leave it in so that it hits about 130 degrees? Thanks much. I was also planning on tossing in some B size red potatoes. Does anyone know a good way to go about it?