have figured out why and can provide a suitable resolution.
Sorry for the lack of pictures, we have mislaid them in the hundreds of mods we have to write up.
We will add them as we find them or just do them again.
What you need is some sound deadening used in PC's that you can stick in place, we have used
some AKASA in the cars we have and this costs about 15 quid for a few sheets which is ample.
Maplin sell it but it will be available online in places such as Ebay.
