I would have rated this at a 5 but give it a 7 as the director actually lived the idea in the plot (director's commentary) and so has first hand knowledge. That fact always gives it a nudge upwards for me as there is truth in the story and not just there for entertainment. Sometimes truth in the story is not compatible with better pacing in a film, but for me reality wins out every time. If it starts to drag a bit, keep at it as the ending is worth the wait.