Well, I guess it depends.
I believe that most people over feed their snakes. I base this on the wild caught corns I have personally seen in the wild. None are really all that huge, and certainly not fat, like many captive corns I have seen, by any stretch of the imagination. Of course, you will sometimes find an animal that wants to push the record books, but they are an anomaly, not the norm.
Seems most people try to pork up their animals, particularly the females, in an effort to get them as big as they can, as quickly as they can, in order to breed them as soon as they can. I'm not real sure that is a real good idea, for the long term health of those females. Even though they may be large enough to pass eggs, are the internal organs matured enough for the stresses of breeding and producing eggs? They don't have the mental capacity to consider such things, but YOU really should.
Also, bear in mind, that just like humans, not all corns will reach the same exact maximum size, no matter how well they are fed. I would say that as an average, corns from the Florida keys area are going to be smaller, as an average, than the average corn you would find in say, Okeetee Plantation. Of course there will always be exceptions to any rule, but again, like people, there will be centralized populations of animals differing from the norm in many ways, including maximum size.
With that being said, can you stunt the growth of an animal by severely underfeeding it? I would have to say that yes, I believe you can. And I also believe that this might have a detrimental effect on the long term health of such an animal from nutrient deficiencies. Baby snakes need calcium to build their skeletal structure. If that calcium is missing or severely restricted, what might be the overall outcome for that animal? My guess would be a weakened skeletal structure. But the point here is that don't have unrealistic expectations of what is "normal" for the growth of a corn snake. Big, fat corn snakes are NOT normal.
Speaking of which, vitamin supplements should be on your list of requirements for your snakes. Yeah, I know, people will say that the captive snakes get everything they need from the whole mice they eat. But are they really? Are the mice getting everything from a dietary standpoint that a wild mice might have available? Hardly. Does this matter to the predators eating them? Quite likely.
This might be particularly important for your breeding females, because they need a LOT more calcium in order to put that extra calcium into the development of the eggs and egg shells during breeding season. If you don't give that to them via dietary supplements, where will it come from? Leached from their own skeletal structure? Perhaps. Just excluded from the development of those eggs and egg shells? Possibly. So are vitamin supplements really a good idea? Yeah, I believe so.
You take on a whole lot of responsibility when you keep captive animals. They are TOTALLY dependent on you for everything they need to be healthy, stay healthy, and thrive. If you breed them, well, you are instigating even more requirements of a dietary and health nature on those females that you really should take into consideration.
Oops, sorry, went off a bit on a tangent.
<soapbox OFF>