I banged my tailgate up pretty good trying to slide my slider back too. It won't go into the slid position without the kingpin mount hitting the tailgate with my setup. No major damage but I did ding things a bit and I wasn't too happy with myself. My slider was a used Curt so I don't have much in it. The problem with dropping the tailgate is you can't turn tight without hitting it into the trailer so it negates the whole reason for the slider. Or at least I assume the tailgate would hit the trailer. I guess I didn't test it.
I'm selling the slider and keeping my Andersen. It's a lot smoother hitch anyway, not to mention better built. I just wish I wouldn't have fooled around with the slider to begin with.