I have killed plenty of birds with the longbow and regular 3 blade heads. A few years back I wanted to try the bullheads. The first morning out I center punched one in the neck, just below the head. It was on film, so I know exactly where I hit. He dropped and jumped up and ran off. Only a few small spots of blood.
I figured it was a fluke, so I went to a different spot on the morning and had the same thing happen! Again, on film. I ended up putting a big Tom down a few hours later with a head shot and a snuffer.
I think with the KE we have with stick bows in the 50 something pound range, a direct center hit in the neck will not get it done with a bullhead. The neck just bends and dosent break. A head shot might do it and a slightly off center hit where the blade hits but not the "field point" part, should work fine. I switched to VPA 3 blades and haven't looked back.