Let me stir the pot with more radical ideas...
I got to thinking, in a physics mindset...does the tungsten REALLY sink faster than lead? Or is it just hype to get people to spend more money? (Oh no, the fly fishing companies would *never* do that!)
The reason I ask is that 2 objects of differing weights and densities will fall (in air) at the same speed, 32 fps, because of gravity. This is, of course, ruling out air resistance. But in the air, a 3" diameter lead sphere and a 3" diameter tungsten sphere will fall at exactly the same rate, which is determined by the fluid displaced, not the object doing the displacing. (Of course, when they hit whatever is below, the tungsten sphere will do more damage, as the force applied at impact *does* vary based on mass.) When you make the switch to water, that value would still be the same for the two objects.
Really, the only benefit to sink rate that I can see is that the higher density of tungsten will give the fly greater inertia as it sinks, making it respond less to the current, however, I believe that this difference would be negligible, or, at very least, a marginal benefit that wouldn't nearly justify the cost.
This just came to me spur of the moment, though, so its possible that I'm leaving out key information. If so, please fill in the blanks. It just seems intuitive that a heavier, denser object would sink faster, but according to Newton, it isn't really the case.