One of my S3's overclocks like a beast!
The other sadly doesn't suffer the same fate! it's hashing at 430 at 218, any higher and the rate drops!
Make sure to keep that beast cool (sub 35C pref), they really don't like getting warm when you run them at 237/250MHz (hash rate starts dropping and you might get and x or two after 10h+ of running)
Unfortunately I cannot get them running much lower temps! they run at 40/42 at stock! it's due to the room temp that I can't get them lower! here is an updated pic of how they look after running overnight!