My solution to prevent scratching was to apply Self adhesive acrylic felt (available in several colours used in craft making projects, lining drawers etc.) firstly to the underside of the plain belt covering edge to edge, then applying a strip to each half of the bonnet just slightly narrower than the belt.
This gives felt to felt contact, i have only applied felt to the curved areas of contact, I have rounded the corners of the strips to prevent the corners lifting.
If it ever needs to removed from the bonnet, soaking in white spirit should loosen the adhesive.
Where the belt contacts the louvers i have used soft velcro dots.
Been in use for 6 months -no sign of wear, or scratching or lifting and does not show when the belt is done up as the two thicknesses of felt are thinner than Lambswoool.
Worth considering?,
Regards jbk
