Dan,
If you read and understood what I wrote, you would realise the problem you are trying to point directly at the 747 is a problem with all aircraft.
As I wrote previously, the V1 calculation is flawed. The data is based on a brand new aircraft, with brand new brakes, brand new tyres and test pilots in the seat. That's not a "normal" line operation. As such, the data is invalid.
I have operated pax aircraft in the same weight range as a fully loaded freighter and the feeling is just the same. It's not a function of the aircraft carrying boxes vs. bums. It's the total weight.
That's why Boeing is so adamant about their "load shedding" philosophy on rejected takeoffs.