Tell ya what I found and you can take it for what it is worth.
I had two wood arrows, same spine, within 15 grains, both RW helical fletch. I put one no mercy RW on one and a LW on the other. Heads were sharpened and weighted with 1 grain of one another. Shot them at 10 yard repeatedly into a new rhinehart broadhead target. Every time the penetration was equal between the two arrows. Apon reading Ashby's reports I would have expected the RW helical arrow with the RW head to out penetrate the other arrow with the LW head. But that was never the case. I know its not animal flesh dead or alive, but it was an equal density object that one should have out penetrated the other. I was impressed on how the arrow rotated into the broadhead target but that was about it.
Like I said, take it for what it is worth. dino