I'm not stressing at all. I did my research and bought accordingly. I only posted above to answer vrocket's question. No need to get fired up over it.
There are a number of folks here who have shimmed their box column 4-post lifts to deal with a sloped floor. As mentioned previously, that ends up requiring ramp modifications as well, as now the cross beam and ramps are raised off the floor. If you search "4 post sloped floor site:
www.garagejournal.com" you can flip through the threads if you're so inclined.
If you're shimming your 4-post, I would advise bolting it down.