I had one of these metal 10,000 rpm ones and it screamed.
It was supposed to flatten out at high rpm, but I don't think it did very much.
I'm just running the stock plastic fan with a non-thermal clutch on it right now. But the fan has stress cracks at the base of every blade.
If the clutch works right, the fan disengages at high rpm and should not even spin.
I think I'll put the Flex-a-lite back on, and if I think it's too noisy, I'll get another plastic one.
I'd like to get one of these:
But I don't want to spend $200 for it, and I don't look forward to wiring it up.