Hi Macgyver,
It sounds like you have calculated the optimum V2 speed for your actual weight (mass), and adjusted the flex temperature for the performance changing effects of QNH, packs etc.
If you then use wet figures and reduce your V1 (to help with the stopping case) but then have an engine failure just afterwards, the adverse effect is that you'll be continuing from a lower speed and take longer to accelerate. In order to clear the 15ft fence at the end of TODA, the V2 is reduced slightly from the optimum previously calculated (but you will still be above V2 min)