my 94 coupe, on Neuspeed Sports and Koni Sports, is about 4.5" from the floor to the stock plastic lip. It's definitely been scraped, but it honestly doesn't happen that often. I mean, if you're trying to drive straight into angled drives and over speed bumps, you're in the wrong anyways.... that's just asking for it. After countless encounters with some odd locations over almost 5 lowered years, it's really a rare occasion when i get major scrapage anymore, anywhere.
And despite that, I will probably never put a front lip on my car, just because it doesn't mix well with what I really want to use my suspension for: driving.