If you are accelerating in a dive, the fuel will remain in the back of the tank. If the fuel level is at least a third full, you will be OK on a modest (non-accelerating) downline. Otherwise, you will usually be OK with the fuel in the lines for several seconds. I guess that there might be an issue with a very long vertical dive where there is minimal acceleration (beyond normal gravitational acceleration). I have never had a flame-out in a dive situation and I would never even consider a clunk line flexible enough to fall to the front of the tank. It's too easy for such a line to kink ot get caught up at the front of the tank.

just my experience.

Ross