That's sweet video. I think that arrow flex is normal. I've seen slow motion video for several other rests and they all flexed like that. I don't know how long the rest is supposed to contact the shaft. On one hand it makes sense that it should stay touching as long as possible without fletching contact. On the other hand, the longer it contacts the rest the more sensitive the arrow is to any kind of flinching / torquing of the grip.