I learned the hard way to not tie down from the bumpers. I had the front bumper tied straight down and the back bumper tied straight down, when we left the straps were really tight, when we got there-not so much, But what wasn't noticed until the next day was that when the straps had started coming loose the sleds suspension started working so it was compressing down making the strap loose, but then when it came back up the strap came tight againm really quick......which ended up causing a bent tunnel. Always tie down from the rails! Superclamps are the way to go if you ask me, front and rear.