NP are big into promoting their boom cut out concept and many other brands have adopted it. Is it a gimmick or benefit????.
I use Pryde sails and the set up seems to work well but it's hard to quantify the level of benefit from this feature alone.

I had a 9m NP RS1 sitting in the garage because I couldn't justify the cost of buying a big carbon boom for it's occasional use. So I went to a sail maker and had the boom cut out, in by 15cm, like my newer Pryde sails.

Did it make a difference?? Well my existing carbon boom now fits nicely.
I used the sail the other day and it felt very different (could be partly my imagination as I have only used the sail twice before on a new board).

The sail felt a little gutless (its probably lost 0.1m under the boom) and I couldn't drive the board upwind. After a bit of fiddling with boom height and mast track I found a setting that worked quite well. However I felt that the sail still didn't seem to be as powerful as before the mod, but I probably need to find the new correct outhaul setting. Overall I was surprised that I needed significant re tuning of the set up.

So what do the experts think about boom cutouts and it's effect on sail performance.