Occasionally I am required to carry out a full power take off in an empty, and I mean empty, aircraft with 5 tonnes of fuel on!
In the above case you need the pitch to control the speed otherwise you get very close to the flap limiting speed before you can say P45.
Why do you need to maintain full power for so long. Reducing power would allow reduced attitude etc. I hope this was performed with a very high SID cap. The vision of a home sick angel comes to mind. It used to be that a regular full power takeoff was required to confirm it was available and test the engine. Surely you don't need to maintain it for the full 5 mins. If not then you could reduce power to something more appropriate. I would have thought full power with a very light a/c was more a test pilot manoeuvre. Full power confirmations could be done easily by a line pilot on a more normal loaded a/c. This occasional testosterone fuelled takeoff might not be allied to the original question, which I'm sure was more line orientated on a normal day.