MIKE !!
I have a deverter you can have.
shoot me a e-mail
I`m sure Ola is aware of most things discussed
he has been around for a long time and flys International events

Here is one thing I learned from Earl Haury

Expanded foam in the Spinner will get rid of the Bell Effect ring, it works

and the most important thing is, the Nose ring .

Experimenting with nose ring/limiters will give you different noises. and levels of noise
I might add if you have to adjust the Motor at all with the nose ring IE force it to fit the Fuse
from firewall missalighnments
you will have motor transfer noises at different rpms mostly mids and highs
more so with composite airplanes.
Apc has a 18+11 med. width blade that they made for a while But no longer distribute
I have a few of these the one inch pich more is a bunch quieter
we might be able to twist there arms alittle to redistribute them
I also have extended and modified many Apc Props with good results pitch , widths and extensions ,
just don`t strike the ground because the tips are more flagile than the rest of the prop
hope this helps
Bryan