That is exactly what I did and on both outward and return journeys I sat jump seat for take off, landing and several hours of that flight - Be understanding though, the pilots do want some time to themselves so be polite and go back to your seat for dinner and the film then return a little later - I cant see them being really mean and saying no! However some are weary because of so-called "Moles" spying on them and telling tales to the press.
Just be realy polite and ask the stewardess when you get on and I'm certain you'll be up there in no time, oh yes, get to the airport early so you are one of the first on the plane so you don't find yourself asking when the cabin crew have a million and one problems and people to sit down.
Good Luck
Speedy