RE: Cutouts - fact or fashion
I am not all convinced that cutouts, contribute directly to board efficiency. This is because the cutouts on most boards leave an irregularly shaped planing surface, with reduced aspect ratio.
A positive effect of cutouts may be that they remove lift from the back of the board, thereby bringing the center of board lift forward. This is important as the center of board lift normally move towards the back, as speed increases.
In other words, a benefit may be that we can keep a well balanced stance in the foot straps, from marginally planing to top speed.