@deckingman In my case, I designed the duct myself for my custom printhead. I ran CFD on it, so I'm happy with where the air is directed. But the CPAP fan at full speed is in another league compared to normal part cooling fans, so there is only so much "containment" of air flow we can do. See the first 15 seconds of Vez3D's video on it. https://youtu.be/E3kBau82SwU?si=skFc90h_gz5UPpWB
He is running his at amazingly high speeds, and even uses extra blowers that direct air from the sides of the print area, which he needs for the high speeds he is running. See this video, it's absolutely astonishing. https://youtu.be/hcMxEkVvIdE?si=Zz3FRlIIbShGoVR1&t=580
So I don't think there is any other option than to use these high powered fans.
I'm running things a bit slower, so I don't need the full power at the moment. But it's nice to know it's there if I do, or if I decide I want to print PLA.
Thankfully the there's no aluminum in the hotend, it's full copper and nichrome. Although the silicone sock would be problematic. The heatbreak is water cooled, so as long as the pump doesn't stop at the same time, the aluminium above the heatbreak wouldn't melt.