Not an expert, Bosse, but I think the best way to get rid of the popping roof is to get a custom fitted one made in a heavier material....Simmond's hood, for example.
The popping sound comes from the two webbing straps that link the hood frames together. They flap against the surface of the hood and make the sound we would rather not hear.
Getting the tension of the hood right has some influence on the noise.
I sometimes wedge a soft cloth between the webbing and the pvc hood. That helps a bit.
