steve, i'm betting an hour will be more than enough. i sure wouldn't cook a wonderful cut like a tenderloin any more than medium rare. in fact, i'd cook it till internal of 125, then pull it, tent with foil, cover it with a couple of towels, and let it rest for about 10 mins. it will cruise up about 10 degrees while it's resting. nothing worse than overcooking a $15/lb piece of meat!!
