Real world, I have implemented ultralite backpacking approach since 05. But I kept the 4 pack so I could carry bulky food water. I also tour in fall where it can be hot or cold, and so I carried more gear for that, and still got caught out. I have tried alternative shelter, so one time I took a tarp vs small tent, and another a tarp vs hammock. So the point is I actually was on average carrying more gear that ultralite, but it didn't bother me. When I got it that light, on a bike, pretty close to sea level, not in the mountains though the daily gain was similar, it was easy anyway, and I want to take full advantage of the bike as a load carrier. I would take a backpack instead probably only if I was planing a trip that combined hiking and riding.