I suggest the use of Denso tape, available from commercial heating merchants. You might want to use two layers. It is very mucky to use, but stays where you put it because of its protective wax. It's 'official' use is to protect underground steel pipes, but if sandwiched between body and chassis it will last longer than the steel it is protecting. I have also used it for wrapping road springs, after cleaning and greasing them properly. Again the job does not need repeating.

Robert Leigh

Location: just north of Cambridge