Be aware that it is a traveller & the wooden frame at the back is fully structural, if the sills are that bad the tinworm will likely extend back under the wood. Taking that off & replacing it if its rotten which is a 99% possibility is a nightmare & horribly expensive. I got my pick up panels from Andrew Eggleton, good quality & good fits. With the availability of good panels its pointless patching these up. Good luck!