You can set share difficulty to what ever you want. If you want 3000 share difficulty just add +3000 to the end off your bitcoin-address-username. When you submit a 3000 difficulty share, it would be the same as if you submitted 3000 difficulty 1 shares. You will see more variance in your stats with higher difficulty shares, but it all works out the same in the end. I haven't tried experimenting with much higher difficulty to see if I get a smaller DOA rate.