I've got the solution for you guys and my Jube too if need be.
Just had a look.
Put a heavy center strip, like a stabilizer bar, from the bottom center bolt on the fender bracket, up to the one top dead center above it. Curve it enough to maximize tire room.
Up on the most vibrational center of the sheet metal above,
thet sets off a higher harmonic frequency . . .
Put a thick rubber block behind the bar,
Drill and tap that location on the bar.
The partially drilled rubber block is held there by a bolt with a fixed washer set back on it that pushes on the rubber.The bolt head side has an extra nut to lock your adjustment and lock the block in place.
You'll actually be able to adjust the sound they still manage to emanate.
You make the prototype, do the patent registration, and we'll go fifty/Fifty
On this the first
Tractor Fender Damper Jubilee
But seriously, I'll bet many others would like to dampen down their fenders on various tractors. Can't be that many tractor fender bracket designs. The vertical damper bar could even be made out of one of those existing adjustable draw bar struts and so it would fit more than one tractor model.
To see how well it will work
put the palm of your left hand in the middle away from the bracket arms, and rap the sheet metal with your knuckles.
You wouldn't have to compromise your tires Tom.