Vspeeds are based on WEIGHT, weight is based on runway length, climb limit, obstacles, brake limits.
If you use an insection for takeoff, the length gets shorter, the obstacles get nearer and the weight changes.
M&V VEF is 1 second prior to V1, if you havent recognized the engine failure at this point and started to react you are going off the end of the runway!
How many of you use a line up distance at the start of the runway?
Mutt