You should be good at 60 stealth actually. I usually use at least 80 though because of passive detect, even on Siege where there is no passive detect, someone with tracking and detect, such as myself, will find and reveal you pretty much every time. At 60 you will reveal almost every time when you get within 5 tiles of someone on production shards, which is not good. If you are training stealth for nefarious reasons, higher is better.