I find the solution to keep this bios and solved my problems.
Using curve in MSI AB I made it to work at constant desired voltage with constant overclock under load.
Default curve designed to use ~1.13v and with +150MHz in MSI AB offset gives ~2050-2100 overclock range.
While I want to use 1v max and stable 2000, I made a line with 2000MHz from 1v to 1.20v and now I have 1v max with 2000MHz
And this 2000 is rock stable and never drops, due to disabled power limits check. On any other bios running 3DMark FSU 1st test or Kombustor drops frequencies due to "hardware" PL on FE cards to about 1900MHz even on 1v on GPU.
So now I happy I got desired level of overclock w/o extra heat and stupid PL drops on other bioses. 1.13v with 2050-2100 made about 50-53C on GPU and now with 2000 1v I have only 40-43C on GPU under full load in real applications/games (45-46C in FSU loop / Kombustor)
MANTAcore
This bios allows up to 1.20v even on FE cards, you just need to make a line with some angle up to this voltage.
Here is how my curve looks:
http://i.imgur.com/APHLSgo.png
This is my FSU with current bios/settings/curve overclock:
NVIDIA GeForce GTX 1080 video card benchmark result - Intel Xeon Processor X5680,ASUSTeK Computer INC. Rampage III Extreme
and here is a result that were made with offset overclock (2100 1.13v):
NVIDIA GeForce GTX 1080 video card benchmark result - Intel Xeon Processor X5680,ASUSTeK Computer INC. Rampage III Extreme
and here is Time Spy:
2000 1v
NVIDIA GeForce GTX 1080 video card benchmark result - Intel Xeon Processor X5680,ASUSTeK Computer INC. Rampage III Extreme
2100 1.13v
NVIDIA GeForce GTX 1080 video card benchmark result - Intel Xeon Processor X5680,ASUSTeK Computer INC. Rampage III Extreme