Rolf, I have never seen sharp edges on the bow of any boat/cat. They are blunt enough not to stall and generate lift when sailing upwind. So cutting them away for aerdynamic reasons is not as clever as some people think. You will find a chapter in Marchaj's book about some of the effects involved.

I have a furling genaker on my boat. I sailed the boat with and without it, never realised any difference, so I don`t care even if it is an easy exercise to calculate it. I wouldn't care about the drag of a snuffer as well, maybe about the blocked airstream to the trampoline. But only if I am bored and want to invent problems
Maybe somebody else has tested his boat with and without snuffer and can us tell the difference?

Cheers,

Klaus