Dan,
By selecting a higher V1 you are using an unbalanced field, the distance required to accelerate with a failed engine from the higher V1 to VR / V2 is shorter than if you were using a Balanced field V1. Therefore you still have the same climb gradient at V2, but the start datum for the climb is not at the end of the runway.
Try to have a look at some Airbus takeoff charts, they love doing this.
Mutt.