If you slip the clutch you're losing ground doing that technically aren't you? I wouldn't bother. I've only managed to land on 6,000rpm in some freakish circumstances (sometimes on a decline down a hill). Always keep the revs up if you wish to stay in the powerband also. It's not possible on paper though as stated before, but different conditions or mods will allow you to do it. In a way, your friend wins the bet as you would be able to land lift by slipping the clutch, but... I mean, slipping the clutch is just ghey. Just shift and slam yO :P