I'll worry about windage once I see the conditions at the time of the competition.
Out of curiousity, slickrock, just how much do you think a 5 mph crosswind (a slight breeze felt on the face) from 3 o'clock will affect a bullet's impact at 1,000 yards relative to your point of aim?
I think that both you and your brother are way out of your leagues with this "wager". Trying to hit a target that is under 1MOA width-wise and barely over 1MOA height-wise at 1,000 yards without ever shooting much past 250?...
Call me a pessimist.... but I would bet that even given 20 rounds each there would not be a hit on paper.