the key to chassis survival was given in the thread "Rebuilding my noddy"date 22/6/10-have a close look.There is a reference "the chassis had been filled with oil".Malcolm marvelled that it was so good wheras the body was poor.Well,the car was mine,& I put a limited quantity of waste engine oil ,using a small squeeze bottle,into each chassis side member,via a body bolt hole.This penetrates into the seams,where rust commences,& creeps upwards to some extent as well.obviously,I did the same to all crossmembers& rear chassis legs.I started doing this to my various Noddys in 1973(yes!)-the results have been fantastic!Start by closing up any rust holes& front subframe drainholes.Have a few containers handy for any small leaks(which-if any will only be slow)Use about one third litre for each side rail for a start.Run front of car up a couple of planks occassionally to get oil to run to rear.used oil best-creeps better!Renault 4 one of the easiest cars to protect in this way(ironically) 165000 hard miles on my car-no chassis rot!