Improved perdigon nymph is a fusion of different tying styles and flies properties. Perdigon sinking rate plus lively partridge legs. It's very easy tie, just pay attention to overlapping body quills to get desired effect and do not soak partridge legs with UV resin.
As for fishing, use thinner tippets since such tippets will improve sinking rate and natural behaviour of the fly. This is perfect fly for all euro nymphing techniques, great for trout, grayling or any other insect feeding fish.
As always, pay attention to the presentation, depth where fish feed....

tight lines

Vladimir