After some initial that were less than satisfactory, I called Bi-Delta and asked for their suggestions on tuning. For a 3 fletch with 4" vanes, the vanes should be oriented with one at 0 degrees, another at 120 and the third at 240. Only the vane at 120 contacts the riser. Using the tip of an exacto knife, separate the perforations in the vane that contacts the riser. Leave the others untouched.
With this done, I have had excellent results. I am using these on 29.5" 2018's, with either 160 grizzlys or 125 zwickeys from a 59# silvertip.