I filled the tank with decor to compensate, don't worry. I've monitored him closely and he's perfectly comfortable (I've seen what he looks like when stressed and it's only happened a couple times over new circumstances like when I put moss in his hide which he did not like). He'll get a T8 sometime next year as his permanent home at any rate.
Speaking of growth though, weighed him today and he's past 200 grams (212 to be exact). Once he's down to his last couple mice I'll get some small rats and see about switching him to those. Plan to try scenting them with a mouse to ease him over, but with how voracious his appetite is I don't think it'll be a problem.