I've been under the car with them a few times, including one time last year with 6 tons jacked up above 20 inches. But I do routinely put the floor jack under the rear diff and put my race ramps under the front wheels. Thinking about picking husky 3 tons from the HD since these were on this list
https://www.garagetooladvisor.com/auto/best-jack-stands very inexpensive and I can't get other jacks stands before this weekend (and not going to be working on the bimmer where you need flat jack point)