my rear end sits lower than yours and im stock . then again i regularly have an extra 12-1300 pounds of people/gear in my car. and my rear shocks are probably blown
you can go lower, a lot lower. at least a 1-0 finger gap. they're coilovers. having more people in the car isn't going to make them compress as much as a normal drop spring and shock combo would. you said yourself that they're stiff. it probably doesn't even move with the two extra people in the car haha.
I thought i was exempt from scraping with two weeks of luck, but scraped over a speed bump (not even a big one) and I was going slow. Watch yourself past -2.0.
My cars lower and I can get over most speed bumps without scraping, I just bottom out on my tires, your stock and driving a truck, you just gotta know how to drive. And as others said you ain't bout that life lol