I've tested a lot of Pascals today with SP_mod#3.
The approach is only 5-7% , according to several different models I have:
1080 FE - 6 cards rig from 330 to 365MH
Palit 1080 GameRock ( Without Premium) - 6 cards rig - from 365 to 384-7MH
Palit 1080 SJS  - 6 cards rig - from 370 to 398 MH
Palit 1070 SJS - 6 cards rig - from 288  to 301 MH

So guess I'll be waiting for this 12% gain ...