"I made a 13 pound roast and like everyone else, was very concerned about the timing.After letting the beef rest at room temp for 1 1/2 hours, I followed directions and after the 1 hour cooking time, my cooking temperature was 58 degrees and thought no way the temp would rise enough in the 3 hour resting period. So, I made the mistake of keeping it in the oven 20 more minutes to 65 degrees. During the resting period, the temperature continued to rise to 130 degrees and by the time I added some heat for 30 minutes, my roast was medium to medium well after the 15 minute rest period. My advice is to follow the directions exactly regardless of the weight. The beef was still very tasty and tender.