I modified my mob grinder in such way that it now collects almost dead monsters in a small 2x2 area. From this area, I allow skeletons to shoot at me. As they shoot, they hit creepers and produce nice amount of music discs.
The problem is that huge portion of arrows still makes it through. I tried to reduce the damage with water, but even 3 blocks of water still aren't enough:
My question therefore is: Can I make such set-up that skeletons will fire me but will never hit me?