How much longer? There is already a lot of space between the rear of the engine and the wheel. I am not sure adding extra "air" there will help from a cosmetic standpoint. Maybe more of a drop seat style to give the impression that it's longer? Who knows, I haven't really gotten started on my XS, well other than the hardtail, so I got a ways to go and a bunch of ideas to try and deal with areas that I don't particularly care for.