I generally start at 40psi and then lower it depending on how slammed I'm getting on rocks/roots. Then I'll go out a week later and almost crash because the tyre flops over when cornering because it's now at 18psi because I didn't check it before I left the house.
According to that chart my pressure is always at least 10psi too low for my weight.. Yet I'd like to go lower for #ukwintergravel riding