I love that landscape!  Certainly looks like a great place for slinging.

I'm still looking into what I should get to measure long distances.  At the moment I'm thinking about one of those measuring wheels you push along the ground.  I've seen them pretty cheap.  Once I have something, I should be able to try some shots like this.

Beautiful scenery.  When I was slinging for my distance record I used Google Earth.  I shot across the mouth of a creek then measured it on the computer.  It was probably a little off but I imagine it was about 90% accurate.  My max ever was 200 yards.  That was a while ago. I doubt I could sling that far now.  I was using smooth, oval shaped river stones then.  If I had used golf balls I know I could have gotten even more distance.