I run a Hans with sliding tethers. Had it for a couple years now and love it. I freaked out before my last race (about a month ago) because I felt like I had too much motion and wondered if I needed a shorter tether. Their website made it sound like I did not. Only issue I have had with mine is that my shoulder belts tend to slide off the Hans. I think the newer models have bigger 'wings' to help with this.
Don't know if this will work or not but here's the race car (Class 10 buggy):
http://instagram.com/p/jYJ_J3Afpy/
-Dave