Personally, I have been keeping baby corns in deli cups as their first cages and definitely feel that the pros outweigh the cons. I have also found that I get more babies to start feeding sooner with them in a confined space with their pinky mouse. Sometimes it is curiosity, and other times irritation at that wiggling pinky mouse that gets them to make that first grab at it. In a larger cage, they might not even find the darn thing or else solve the irritation problem by just going over to the opposite side of the cage.
Getting ready for a show is MUCH easier now than it used to be. Just picking out the deli cups and loading them into the styros takes a whole lot less time than transferring them from a shoebox to a deli cup and then transferring the unsold ones back there when we get back.
I can't remember when I actually first went to the deli cup rack system for my babies, but I believe I may even have an entire generation (or maybe two?) that were raised this way that are now breeding fine and proof positive that it is not detrimental to their health in any manner I can determine. Of course, there are always going to be a few that will resent being in a smaller cage, but I have found that putting them in a larger cage only delays their pushing at the lid until they get big enough to do that there as well. The few snakes I get that get damaged noses is more because of the company that drills the holes in the deli cups doing it in such a manner that the rough edges are on the inside rather than the outside of the deli cup bottoms.
I have kept baby corns in deli cups an embarrassingly long period of time and in most cases they do not care at all. If I could, I would certainly move them to larger cages more quickly than I do, but all things considered, this has been one of the best ideas I have ever come up with. There is just no other way I could maintain the number of babies I do every season without it.
Since I am in this business for the long haul, and many of the babies I produce are for my own breeding stock, certainly if I felt this method were detrimental to the health of the animals, I would have no other choice but to find a different, better solution to keeping all of those babies.
IMHO.