I am cooking an 8 lb beef top butt roast. At least that is what I think it is. I is choice angus and in a cryovac. The neighbor works at a food warehouse and one of the drivers gave it to him. It has a small fat cap on the bottom and is round like a ball, not flat. Anyway, I plan to cook the interior to 135 and slice for sandwiches. How long do you anticipate it will take to get to 135 inside. As always, thanks in advance for all your help. Note: I would take a pic but my wife has the camera in her purse and she is out shopping. Thanks again.