One thing I didn't add in the single bevel/double bevel conversation is, from all my testing and live game experience with low poundage bows, I believe it is the razor sharp tip point of the double bevel that seems to make the big difference, when shooting low weight draws.
While single bevels may be great with bows 50lbs to the 60-80lb bows tested on African game or USA game with high weights, with 40lbs, the duller point of most single bevels cut about well as a blunt hammer head.
Now, perhaps a single bevel with a razor sharp tip may work as well, but keep in mind that the KE of low weight bows have little to give up, before performance really suffers.
I also found that a 3 blade, even a razor sharp point like a NAP Razor Cap, had poor penetration compared to double bevels. Granted, I killed deer with the Razor Cap, but the head just went into the center of the heart/chest (on small, young fawn deer with antlerless tags-and zero passthru shots), where Stingers, Phat Heads and Silver Flames have all skipped away with easy passthru shots.
Again, just my experience with 60 some bows in the low weight range and several 100 kills.