update:
now that i’m jamming on headphones and not on a very quiet practice amp, it seems that my 2k pot wired to R5 is controlling the bias (sound seems to get very velcro-ish when i reduce it) and the sag actually works great here imo. i changed the C1 mod to be 100n/10n and the bass reduction at 10n is really nice. still can’t wrap my head around the C3 toggle, it’s as recommended in the OKF doc (220n/22n) but i can’t hear the difference. anyway this thing is badass!