Suitable size tank for Coastal Python

[PythonNoobe]

Currently 60cm came in a 30cm cube. What length is too long for this tank?

Is there any problem in setting up a 120x60x120cm (reptile one what do people think of these? seems ok for 450$) and putting the 30cm tank inside with access to the bigger tank? Im thinking of splitting the 120cm tank in half to start with and possibly putting another snake on the other side. Lights and heat will be lowered down to the needed height inside the tank.

Is growth encourage by big area? held back by small area?
Is too much room a bad thing?

Thanks