Anyway, I switched the last (good) hboard to the other two that didnt perform so well (16gh each), and the magic happend: 60gh coming out of these babies. Nice. Same settings for the first 32 chips (with autotune off, I tweaked it a little bit last night, but with not too good results). The third board is autotune on, performing 17.452GH/s, 19.9GH/s, 23.336GH/s. Still some more tweaking to be done, but I'm fine for now