I just installed some Bohning Blazer Stretch Fletch helical vanes on some 350 Maxima Blue Streak arrows. They are advertised as 3 degree helical, however I twisted them up to make the helical considerably more aggressive than that. I estimate they are more like 6 to 8 degree helical.
I shot them through a WB rest (with large apperature) and they shoot well, and should stabilize a broadhead quickly. I did a speed comparison with identical arrows with offset blazers, and found the following results.
Using an APA M6, set at 55#, with 400 grain arrows and a 28" draw, the offset arrows came off the bow at 274 fps, and the helical at 267 fps. This would be attributed to the extra drag through the rest. At 50 yds, the offsets were at 251 fps, and the helicals at 243 fps. I was surprised that the helicals didn't lose more speed at 50 yds, only trailing the offset blazers by 8 fps, and 7 of the 8 was lost to getting through the WB. I can't comment on the longevity of the WB or the vanes yet, but will post back after shooting a bunch more arrows. The Stretch Fletch vanes seem extemely tough however, and I will be surprised if they show much wear. They are heavier, as they are one piece construction, and this extra weight on the back took my FOC from 11.4 to 8.8, compared with the offset Blazers.