Here is what I have found by shooting the crono at our shop:

String Leach -3 to 4 fps, Cat Wiskers -up to 6 fps depending on the length, Stabalizers Very small amounts with several models no more than -1 or 2 fps, My huge peep -2 fps, string loop -0 fps.

I tryed Leaches and Whiskers on the cables and lost little if any speed.

It seems there is a sweet spot with the whiskers on the cables as you may have to play with it to get the desired effect.

With all the "stuff" on my string I only lost about 9 fps with my fianal set-up.I think this is a small price to pay for a whisper compared to a drum.

You may find these figures to be off a little with your particular set-up but not by much.

Hope this helps
SF