ORIGINAL: davidmil
Smoke and mirrors. I think the comments on you tube are dead on. They end up holding the cables in a static position increasing poundage. The cable slide is no longer a cable slide but instead another pivot point.
Correct. Not only that but I would guess that by pulling the cables forward it also rotates the cams a little farther increasing the draw length. Couple the two together and I could easily see 15 to 20 fps increase, but then the bow doesn't fit me any more.
Do have to admit that if someone with a regular guarded bow has an itch to get some sort of roller guard this would be an easy way to do it. And it could be moved from bow to bow as bows get replaced. It just may reduce noise from cable vibration, too, so it might not be all bad.
An example of what you just said: Martin just came out with a roller guard this year on some of it's Pro series bows. They actually state that the roller guard increases the bow poundage by approximately 5# over a regular rod and slide, assuming the same limbs.
I'm sure we'll see some of them around sooner or later.