ORIGINAL: Roberto B.
Derek,
Looking at the picture inside the fuse toward the tail, i can see the inner fiberglass layer that present a non uniform colour.
I have the suspect that the lighter areas could have a weak bonding to the foam. I hope it's only a matter of light effect instead.
Roberto,
I hope you are wrong!
It seems pretty stiff and there doesn't appear to be any breakdown of the fiberglass in those areas.