Yeah, they're a difficult lot. We did not have them in Sweden until they managed to survive around the warm water outlets of our coastal nuclear plants around 20 years ago. I have targeted them and caught a few, including a record 6.12kg fish on a size 16 dry fly. I often see them cruising along the shore, showing dorsal fins and upper lips as if they are engulfing things on the surface. Whether they sometimes  take a small dry fly by mistake, I don't know. Over the years I've probably spent 40+ hours per fish caught. I was in contact with a guy in the Channel Islands who said he used small "lumis" at night successfully. I have not tried it. I know there are people who use scented green algae-like flies. Success???