Why still no dive acceleration difference?

[Crumpp]

I don't believe that.

So?

For all of WWI airfoils(RAF6,ClarkY,Gottingen), 4-blade design is useless, but for the newly developed NACA16, story is different.

Did you read the NACA's own findings on the Clark Y and NACA 16 series?

The 16 series has poor lift production and its only real application was in propellers. It was generally considered to be worse than the Clark Y even in that application. The NACA 16 series was supposed be low drag at high speed and designed for the very high transonic realm. It was a real disappointment to the NACA.

Go back a few pages and re-read it. It will confirm there was no difference at speed and the Clark Y was actually better overall.