I have this card. I'm not a strapmeister. I can achieve 30+ with an explanation.

 BIOS strapping 101: copy the 1750 strap over the higher straps. 28+ mh/s

Luck:

After reading all the relevant 580 threads, treasure can be found in the AMD rebrand thread that can get this card to 30+. But......, the drawback is that this card uses more power.