I've used Singh Ray resin filters for years but am really quite unhappy with how easily they scratch. Obviously, along the edges, they scratch the very first time I ever insert them into the Cokin P holder system, but I've also scratched them using a lens cloth and even at times it seems when putting them into and out of the provided holder. Once they're scratched, obviously image quality begins to suffer. What are your thoughts on the many graduated "P" sized (4"x6") filters available from Lee, Tiffen, etc? Which do you find the most durable? Am I the only one who's experienced the Singh Ray filters scratching this easily?