I just got a Bitzenburger also. I really like the quality, and the way it works. I only have the straight clamp, which can be adjusted for offset, which is how I have been fletching arrows. It is much better than my BPE fletcher.
My eperience with helical clamps is that you generally have to set the offset so that the fletch is in good contact with the arrow. If you try to use less offset, or " straighten out" the fletch with a helical clamp, the center portion of the fletching will not come in contact with the arrow. The ends will contact the shaft, and there wil be a gap in the middle. I have gotten around that by putting the fletch in the clamp, and spreading the ends of the fletch with my left thumb and index finger, while I was lightly spreading the jaws of the fletching clamp with the right hand. This would cause the middle of the fletch to pull below the actual bottom of the fletching clamp. I would then put the clamp on the jig, and press clamp down on the arrow while again pressing lightly on the clamp " handles." This allows the fletch to conform to the arrow shaft. Then let the clamp go so it again grips the fletch. Pull it off, put the fletching cement on the vane, then put the clamp on the jig as normal. It works, but it was just about as much of a pain as it sounds like. I did this mostly with skinny carbons to use with shoot through rests. If I had a straight clamp at the time, it would have been much easier.