Heavy jet operation re: V2

[backin5]

Any heavy jet pilots out there, any thoughts?... I'm trying to et my head around the complexities of V-speeds!!

If after normal rotation on a normal (4 engine) heavy weight take off the aircraft has not reached V2 would you maintain a slightly lower nose attitude to increase speed to V2, or continue rotation and fly below V2 and count on acceleration in the climb?

Would you consider increasing thrust if it were available?
Is flying below V2 on initial climb out unsafe?

Could you assume that the aircraft loading data was probably incorrect and that the aircraft was actually heavier than what the figures had been calculated for?

Does this kind of underperformance occur regularly?

Thanks.