I think a lot of what we perceive of as 'a slippery aeroplane' probably has more to do with high idle thrust settings on the engines rather than low drag fuselages, with the 747 big fans having possibly a higher inflight idle thrust setting due to the historic problems with big fans sometimes not responding to thrust lever demands. Certainly with the 747, once the flaps are mostly out, and all those wheels down, it becomes a flying brick!