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FYI, the standard wisdom for juvi/mature terrestrials is 2-3X the size of the T in both horizontal dimensions but it does sometimes depend on the species. I agree with Ratmosphere that you're running a little small with that enclosure, especially since your animal still has some growing to do.
I generally like to go a little bigger than recommended (+50%) but I've got the space for it. I also like to adjust the enclosure size depending on the personality of the species. For fire-breathers I tend to oversize by a good amount to give them room to comfortably retreat during enclosure maintenance.
One often over-looked aspect of enclosure size is decoration. Everything that you put in the enclosure takes up space the T would normally have. Don't forget to adjust the enclosure size to account for plants, skulls, original edition Star Wars figurines, miniature cars, and other miscellaneous toys you add to the environment.