I'm pretty low and my cans don't scrape, even driving around San Diego, where nothing is flat and level. Just use the same precautions as you normally would with a lower car... if something is steep, angle the car up it.

For HFCs it depends, I don't think my Berks pass CA smog, not that it matters because they have a ridiculous policy on emissions modification. Kinetix I think guarantees a pass in a CA smog check, but it's not going to pass if a cop snags you and tells you to visit the inspection ref. I pass NV smog fine though, and they generally don't care what you do to the car as long as you pass. HFCs should pass just fine in most states though.