@snakeboy: nice to hear that your 'gums' lasted 40k km- my colleague has reached 30k and it still fits .
@pepsi: thanks! the simple things are mostly useful.
@mb4807: the optimal thickness would be 1.2mm - i wasn't getting a sheet with this dimesion in my local shop, so i made my 1.3 mm sheet and pressed them together with glue to get it. one piece of 1.2 mm would be perfect.

left hand greets from Switzerland

Andy