Whats a Sustainable Winrate for 6max 50$ PLO

What would you say is an average/high winrate/BB for a Winning Omaha 50$ 6-max level? Is it possible to sustain a 21bb/100 or am i just pushing my luck? What kinds of winrates are you guys getting at or around these levels and what would be a more practicle winrate to look forward to? (that is if 21bb/100 is outragous, i really dont know)