Hi, First I thought I would mention if you want to get more morphs later have you considered a rack set up with tubs. You could talk to some of the folks here that have a real good knowledge of this type housing (and search.) But maybe that would be something you would rather do down the road, or not at all. If so I would go ahead and buy the larger 36x24x24 size. The hide size is the most important thing anyway and they can grow pretty fast, ( I bought mine in april it was pretty small and is now a 414 gram snake.) and you can always cover the front and sides with colored paper (I did this at first, but later removed it) and when you put 2 hides, and a good sized water bowl and maybe some thing to climb on you might wonder if it will be big enough, (it should be). I like to leave a little space to wrap up if feeding in the enclosure anyway. I would then put the larger snake in the 40. This will really save you money in the long run. Because as your snakes grow you will really wish you had gotten the larger size. But like I say if you're going to add, you might wish you had went to the rack and tubs to save money and space in the long run.