I didnt know you had this guy Rob! very nice. U can see it is getting real chunky.
I 'd say it looks 9 - 10 inch based on how thick he is.
and yes, AT' s have very little height growth, unlike IT, ST . (NTT and NGT have sim,ilar height growths, not as much as IT & ST). I reckon itll be 2 years till its 12 inch.