I have a pair of Simms G4's with Vibram, they have saved my butt several times. The slickest river bottom that I've been around is at Roaring River down from the park at the conservation area. I think a few on here can a agree its slick. I have fished it with both felt and Vibrams, and the Vibrams (without studs) gripped far better than the felt. And the best part about Vibrams in my opinion is I can put them in the back of my car and they will be dry by the time that I'm home without soaking the carpet.