I am also interested in the walther. It's not a gun I would modify much as the appeal to me is the lifetime warranty. I have heard the trigger is a little sloppy but can't verify that. Should be an interesting thread.
Its a Umarex RWS Hammerli 850 converted to HPA bottle gun like Roalds retired 850 store from the factory with a blinged out wooden stock and hopefully better 8 shot magazines like the Maxima Thor air tube version.