On most of my bows, I don't see a huge difference with real light arrows, but it is noticable.

My strings are usually the recommended 16 strands, for Ultracam. In my opinion, the Catfish loop helps a lot. It is connected rather loosely and I think it helps absorb vibration in the most critical spot on the string - the middle. I don't think I lose much speed at all, because I have so little weight on the middle of the string. The heavier arrows are not the result of wanting a quieter bow, they are that way because I want a slightly stiffer spine and a high FOC. This just happens to make my arrow fall in the 450-500 grain range. I'm usually drawing anywhere from 60-65 lbs. I might lose a couple fps with the Biscuit and the cable dampener placement, but it's insignificant in my opinion.