Well it is possible, but it's not easy after a certain point. Anything older than 4.5 is going to be pretty difficult to age on the hoof. There's an article in the land mgt. issue of D&DH that Alshiemer wrote that might help you out. But it can be done with younger deer easier. Smaller rack is basically most the time going to lead to a 1.5 or 2.5 depending on nutrition and the health of your deer herd. 1.5-2.5 normally wont have more than 10 points at the very most and typically and wont have much mass, Those deer will also have a thiner neck, longer legs for their body, a smaller leaner stomach and a shorter snout. Older deer some 2.5 and 3.5-4.5 will fill out more, having larger necks that kind of look like they just blend into the rest of the body of the deer, the legs in the older deer will look shorter for its body and it might look like the deer is walking more choppier than the younger deer, the snout will be longer and the deer's stomach will be saggier, (like he has a gut) on the older deer. Darker Tarsal glands are also a sign of a more mature deer, the darker the older. Thier are other variables as well, but i recommend getting that issue for a reference if you want more info. Hope i helped!