After deglazing the pan with Port, the recipes calls for wine, porcini liquid, and rosemary to be added and reduced. Does anyone consider adding b...

All things being equal except length, roasting time won't change much if at all. Time-per-pound estimates assume the object in question will get larger proportionally as the weight goes up (as would a chicken or turkey). Outside of attempting to coordinate time of service, relying on them is a really good way of wrecking an expensive cut of meat. As Pierino always says, it's done when it's done. And as I like to say, the only way of knowing for sure is to stick a thermometer in it.

You should really go by temperature but depending on it's size it might take about 15 minutes.

Ok I never understand this. This recipe call for 3 pounds, to much. So if I buy 1 1/2 - 2 pounds how do I adjust the timing. It would be the same diameter but ??

Beef stock would be a good substitute for the mushroom stock.

You could probably use beef broth/stock in place of the wine or porcini liquid if you wanted.