Last year I did a ton of experiments and arrived at 80g coffee per 1400g water (48 fl oz, a big press pot). This is 5.7% by weight relative to the water. I'm mostly buying East African coffees, especially Ethiopian varieties, from 3rd wave roasters who favor a lighter roast. Occasionally I'll end up with beans that do better with 90g or 70g, but this is rare.
The variable that took me forever to figure out was water temperature. About 8 years ago in this thread I was complaining that the coffee I made at my girlfriend's apartment, with a crappy grinder and no scale, was often better than what I made at home while geeking out. The culprit turned out to be my (supposedly fancy) Zojirushi hot water pot, which was set to 203°F. Turns out that it was about 10 degrees cooler than that, and this was throwing off everything.
I use a regular electric kettle now and check the temperature. After trying every temperature in the recommended range, I found 93°C / 199°F to be my favorite. My press pot is uninsulated, so this would be the starting temperature. I've never measured to see how much it drops over 4 minutes.
