Another vote for Silentcoat , I used 2mm it’s surprising heavy , if the surface has been degreased silentcoat will stick . I used a heat gun to warm up the coat which helps with moulding round contours etc . A wall paper roller (2ins) is good for getting the silent coat to adhere to tight corners . I used silentcoat for the boot floor , cabin, bulkhead , doors , gearbox cover in my Vitesse
Paul