I'm a pretty serious snake keeper, and I'm not going to claim exception to BloodyIrish's statement about frowning on keeping snakes together. I have it on the authority of several respected snake breeders as well as my own personal experience that it is better to avoid it. Yes, it *can* work, but I strongly feel it's not worth the risk to the snakes to attempt to keep them together, even just to see how it goes, and I hope those who truly care about their snakese and wish the best for them will agree. You say there's nothing wrong with it except the extra work. Keep two snakes in separate cages rather than a single cage and you still have the same amount of snake poop to clean up, plus you have the added benefit of relatively easy feeding procedures and record-keeping, if you're into that kind of thing. Plus you don't have to worry about one snake eating the other, or one snake getting over-stressed by the other, more-dominant snake, and thus going off feed and being more prone to infection. Also, I think dividers count as separate cages.
So in the end, it comes down to whether the keeper is willing to risk the health of the snakes because he or she doesn't feeling like getting another cage.
Just because I don't volunteer at a nature center doesn't mean I don't know what I'm talking about, either.
Okay, now back to the topic of the thread: corn snake enclosures. If you keep an adult in a 55 or 75, the snake will definitely utilize the entire cage. Corns are pretty active and like to flex their muscles a lot. I just keep my corn on flat sheets of newspaper with some more newspaper torn into long strips and he loves burrowing under them. But if you want to do a full vivarium kind of thing with live plants and active biocultures in the soil, that could be pretty amazing. Harder to set up initially, but the payoff would be great
What kind of setup are you looking to do anyway? Utilitarian or natural?
And, I don't know what the climate where you live is like, except that it's colder than where I live. My corn stays in a room that gets no AC in the summer, so the temps can get up to around 90 in the day, and it's heated during the day in the winter so it'll get up to 68 in the day and 50-55 at night. I've never used supplemental heat on him and I've never had any problems, but you might be better off with a lamp or heat panel where you live.
Anymore questions and I'll be glad to help you anyway I can.