What impact on board size requirement do different cambers have?

When getting a reverse camber/ rockered board you generally size down, because the board has more float or support in the snow. This means that it would take less board to give to same amount of support/ float in the snow. If you weigh 160 you should get a board about 155-160. Because it is a banana you should get a 155 for freestyle, a 157 for all mountain, or a 159-160 for pow.