yeh my vinyl was upholsterers vinyl, pretty stretchy and only a bit of cotton backing.
hahah, glad to hear i dont have negative camber anymore

jono, joins were pretty easy, pretty much did what waldo did in the tech article (cut along the top of the seam of where the black and the old grey vinyl meet) left a bit of an overlap of the blue under the black, and used 'ksbond' glue on both surfaces, left till tacky then pressed down. wallah! seams done.
i did use wadding behind the vinyl to give it a professional feel/look too i don't think waldo did.