The risers have set screws so that the bars will not move. Use bushings. I ahve had no issues with mine in nearly a year and I ride a lot. the set screws hold them rock solid. there is no need for a one piece clamp due to the set screws. I guess the guy didn't really look at the risers...
I have 14" Carlini Fly'in Apes on my 2004 Fatboy. They are the 1.5" bars with the matching piston risers and I use the poly bushings. They are solid as a rock. No slipping or problems of any kind what so ever.
+1 - same set-up (though 16" bars) and no problems whatsoever.