Len, you have to take the entire package when discussing his work, not just snippets. Did you read the part about faster arrows encountering increased resistance? Resistance is geometrically proportional to the arrow's speed. Meaning a lighter arrow that's travelling twice as fast as a heavy arrow will encounter resistance 4 times that of the slower, heavier arrow. If it could be shot 4 times faster it would encounter 16 times the resistance. That's why he says increasing momentum by increasing speed is not equivalent to increasing momentum with weight. The faster arrow will encounter more resistance. The slower arrow will encounter less resistance. (That's the fallacy in TFOX's thinking that driving an arrow faster will help it overcome friction. Quite the reverse is true.)

Even ballistics programs show the difference in the different rates of speed KE lost over distance while cutting through thin air to the target. Lower speed (w/heavier arrow) = lower resistance = higher percentage of retained energy = increased penetration potential. Higher speed (w/lighter arrow) = more resistance = lesser percentage of retained energy = less penetration potential. The smaller diameter and superior damping qualities of carbon help cancel out some of that increased resistance, perhaps, but still, it's the cutting edges on the broadhead blades that encounter the lion's share of the resistance. So, you'd have to shoot a smaller diameter head with fewer blades on fast arrows to significantly offset that increased resistance.

Again, with smaller, thin skinned animals like deer, it's not likely to be that big a deal. On larger, tougher game though, it would be more noticeable.