That is pretty much as big as Sumo gets.....you must have been doing something right :D.... If you wanted to get anything bigger than that you'd pretty much be stuck with Atlantic Giant (which will get to 1500 lbs in this country) but they can be sods to get growing by all accounts whereas Sumo (and Hundreweight and Big Max) might top out at around 200lbs buit at least won't just randomly die on you in the first month....
chrisc