I used to operate 747 Classics for many years, all of which were 'packs-off' takeoffs...
I'm still trying to get around this 'pressure bump' you guys are talking about...
All 3 packs off until around 200', then 1 pack on, then 2nd pack on when stabilized in the climb, followed by the 3rd, again, after.....
Then one pack off during the cruise.
I don't know what all this 'pressure-bump' is about, it was never a problem, worked just fine, and was ultra-reliable...
EW73