I've never used them. I bought a package of the Helix heads earlier this year to play with. They do fly well as I've shot them to 60 yards thus far and they hit right along with my Slick Trick Razor Tricks. I don't think they are as forgiving as the smaller profile heads. When I first got them they were not shooting well, and the Trick's were, but after doing some fine tuning on me and the bow problem solved.
If you believe all the Ashby stuff they are far superior than a double bevel. The concept is good but not really proven. Not sure there is a significant difference between the two. Both are good heads.