hmmm.... that one took an extra bite of deer sausage to mull over!

OK, if I'm understanding your query right -- and I think I am -- the speedat which the action of the blades opening might change based on arrow speed, but the distance the arrow travels while opening would remain the same. I'll try to explain.

If the point of the blade has to come into contact with, let's say, deer hide, and that medium grabs the point and starts leveraging it backwards to open the blade into its full-width cutting diamter (I'm thinking of my Rocket Aeroheads here), it really doesn't matter how fast or slow the arrow is travelling -- just that the arrow has enough kinetic energy to absorb that action (and the resulting loss of energy absorbed by that act) and keep on trucking through. Whether that action happens quickly or on a more slower basis should be a moot point; it would happen in the same distance.

Is that kinda what you were thinking about?