Best settings so far for my oct jupiter (4 VRM):

FW: 0.99.1-tune (oct)
OC: 231
Advanced tuning: None (default from stock version) see "Other findings"

Before OC:
Avg.HR: 560 Gh/s, poolside: 520-530 Gh/s
WU: 8045
HW err%: 3%
Pool rejects%: 0.6%
Watts: 550 W (bertmod)

After OC:
Avg.HR: 650 Gh/s, poolside: 620-640 Gh/s
WU: 9083
HW err%: 5-7%
Pool rejects%: 0.9%
Watts: 680-690 W (bertmod)
ASIC1: 56.0 ℃ , avg 53 Amps
ASIC2: 42.0 ℃ , avg 52 Amps
ASIC3: 61.5 ℃ , avg 56 Amps (highest die: 61 Amps)
ASIC4: 51.5 ℃ , avg 54 Amps

Other findings:

I've played a lot with the Advanced tuning part with different SPI volt,freq and individual die-voltage settings.
The 'trick' is to get the Amps between 50-55 for ultimate power/Gh ratio (correct me if i'm wrong).
After days of experimenting it came down to what hno (from irc) once said: it's like chasing ghosts!

At the end the default-settings for Advanced tuning works best (for now), BUT after playing with those
settings, and at the end setting all the Advanced tuner settings back to original values(manually) resulted in the worst performance of 250 Gh/s and the only remedy was to reflash the FW.
I'll play again with the settings after next diff change.

Btw, a lot of thanks to all contributers in this thread and to iterate Cablez's remark:
"Wonderful thread gentlemen, really shows the pioneering spirit of the mining core. Thank you."

and last but certainly not least: OP (1NT4RyJMqtRuDRr6zHdXdKSpmX3SR5he6z) and tolip_wen (13362fxFAdrhagmCvSmFy4WoHrNRPG2V57) !