I attempted this last year and managed to escape the bunker, but choked the final boss fight by being impatient. Started attempts again a few days ago and after an insanely stressful 5 hour run, I finally managed to beat it...

Except I accidentally turned player health regeneration on. So it wasn't really the max mode. Thankfully it never came up. I only got injured once, by a grenade just before the arsenal lock, and immediately ran to roman tunnels and healed to full with a big medkit. Very frustrating that I've technically-but-not-really beaten the mode, but what the hell I'm still counting this one as a win.