How old is the python? That would suit a hatchy nicely for a few years. But remember floor space is a lot more important than height with stimies as they hardly climb.
the next size up is the way to go for a stimi. I have mine in a 90cm long one, and it wouldn't want to be any smaller. Stimi's can still get to a desent length.
That is about the same size as my set up for my Mac (600x300x400) and as far as I have found Stimi's are very similar. Skittles will be 2 this Dec and is currently 1.1m, she is very content in her enclosure. I have been told by any number of people that Hatchies will do better in a click cluntil they get some size on them although I have heard of people having success with larger tanks provided there is plenty of cover for them to move between and several hides in the different temp zones If you are buying a yearling or at least more than 6 months old it should be fine.
Stimilove's comment is fair enough if you didn't already have a tank but the size you have will see you out of a lot of trouble and then you can save up for a larger setup down the track. One of the best things I added was a Magtech rock ledge which Skittles loves to climb up on and chill out, they are more rock climbers than branch dwellers.
These are some old pics I'll try to get one when I get home again of the current setup with a few more plants and the rock ledge. A friend with 30+ years experience in all aspects of herping came over the other day and commented on how content she is and how she is thriving. The tank will do her for quite a while yet although when she is closer to fully grown I want to upgrade to a tank approximately 1000x400x500 with a series of rock ledges to move between. She will reach 1.5-1.6m at full size.
Well here are two shots taken today while Skittles was enjoying her rock ledge...
BTW to help maintain your temp in a glass tank line three sides with something, I used plastic fishtank background on the outside and if it was still an issue I was going to use a thin layer of styrofoam but whether the lining was enough or because it's set in a wall unit my temp range has never been an issue.
