Stator Vane,
Firstly the answer to your V-speed question is as follows: Most of the existing wet runway performance adjustments are based on an assumption that the wet braking mu is one half of the dry mu. However at higher weights and speeds the dry mu starts to decrease so the margin between the dry mu and the wet mu (which is established at lower wts and speeds) gets smaller because the wet mu is constant.
Thats straight from Boeing.
As for the flaps, how about For some airplanes there may be an altitude placard for flaps down operation since it may be possible to exceed limit loads when applying maximum roll capability. Tie that up with FAR 25.341 and 335 and hopefully you will get your answer
Mutt