Back in the 1980's, there was a 747 taking off from London (Heathrow I think - it's been quite a while). Anyway, they over rotated quite badly and both outboard engines surged and did not recover. They managed to circle around and land on two engines, dumping fuel the entire time
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A guy that used to drive KC135s told me that the original turbojet powered airplane (prior to the engine retrofit) takeoff performance was so marginal that if they lost an engine after V1, there was a handle the flight engineer could pull to start dumping fuel out the refueling drogue at whatever the max fuel transfer rate was.
I'm sure the original question was about the 'legal' fuel dump altitude - just pointing out that sometimes you need to do what you need to do
