sgminer.exe -k groestlcoin -o stratum+tcp://cryptohunger.com:3333 -u x.x -p x -I 20 -g 1 -w 256 --thread-concurrency 8192 --gpu-engine 1200 --gpu-memclock 1600 --lookup-gap 0 --gpu-fan 55-75 --difficulty-multiplier 0.0039062500
pause

I used this config, and it works. Yes, I'm using 4.1.The difficulty command does matter 0MH without it.

Asus 280x