Actually my research has found that you can go up around -1.0. I cant find the chart but I had found that listed things we do everyday, one of them included plopping down on a couch and registering something like 10+ G's. Negative they gave some examples of hitting -1.2, but again, briefly. Nothing sustained and nothing TOO sudden either.
The thing everyone here, and usually elsewhere forgets it the length of TIME that you hold those G's. If you want to hit 5-6 G's, only for a second. Even 3-4G's if held for more than 3 seconds can black someone out (Think Goliath SFMM)
Negative G's work the same way, but less leeway. You can hit -1 but only for a brief second. Like, the very apex of a hill. If you somehow were to hit -1 and then hold it for 2-3 seconds, people would be redding out, which is far more worse than blacking out.