My buddy installed the full Frogskinz package on his SXR while doing a rebuild and a few other mods. Having them all installed caused the ski to run poorly and there was a whistle while riding. We chased all kinds of phantom issues, thinking the whistle was some kind of bearing noise, but he noted that it ran fine on the trailer (while the hood was off), so we began searching for other issues. He finally found that the Frogskinz were not allowing enough air into the engine compartment, as the screens were fairly restrictive. He removed one of the screens, and the ski immediately ran fine on the water, and the whistle was gone.
On the plus side, they are VERY effective at keeping stuff out of your engine compartment, including air.