Yer he is only 5 mths old, the enclosure is 3 ft so he will last in it for a while... Once he out grows it I'll put my spotted in there and buy my coastal the next size up witch is 4ft. Hopefully the 4 ft will do him for his life.if not I'll get a larger enclosure.
i'd bypass the 4ft and plan on the larger enclosure now rather than later, the chance of a full grown coastal being comfortable in a 4ft enclosure are slim, there are a lot that get to 8-9ft, some managed 12ft ! !