I have said this so many times .. the BM1373's should NOT be push above 3-4TH and 4TH is the MAX MAX IMO ..
3-3.5TH is best with good cooling, not because the BM1373 chip can be pushed upto 6TH does not means its a good idea!!, if the efficiency is worse than a few BM1370's then DO NOT push it that high its pointless, best to use many cheap BM1370 chips instead.
My P2 is setup for 7TH @ 92w at the WALL and VR temps in the 50's; miner is 100% stock and to me thats close to max tune for only 2x BM1373 chips.
I also have a good 8.1TH tune as well but don't care to waste 32w just for 1TH more and i have a sweet 5.5TH tune crazy how cool the miner runs when within proper operational specs of the chip!!
To me the true point of the BM1373 chips, is to run cool and extremely efficient !! NOT to be pushed because they can ..