Besides as J T said, perf figures are for a prescribed set of circumstances, as you have to base them on something. It's just that it is pretty unlikely you will have those circumstances afffecting you on the day you hear ""RING RING" " V1", and as John Coleman said " What happened next"" answers to..
I assume that instead of going for the pint point intersection in the stop/go curve, it would be sensible to reduce weight a little and then go for the point between the most optimistic and most pesimistic V1s?