I used to catch plenty on crankbaits and plastics but didn't target them with the fly. I know a lot of fly anglers think perch're just easy because they accidentally catch them sometimes, but that's a nonsense-if you follow the reasoning then trout are easier because they catch more trout over the season. Also, they tend not to be catching 3lbers, 6 inch schoolies don't count..unless that's your thing, then they do. Accidental captures just don't really tell you anything about a species other than that occasionally that technique might work for them.
I love perch fishing, I think they're a real impressive fish when they get big, with they're spikes, stripes and bristly attitude. And they're not easy if you're targetting big fish with big flies. Scaling up the fly to 7.5 or maybe even 10cm will cut out a lot of the small fish which is fine, but it means you probably want wire if pike are present. This really cuts perch catches in my experience, but it also stops you leaving hooks in pike and losing all your flies. It's a trade of I'm willing to make, I'd rather fish for 1 or 2 fish of 40cm or there abouts than 20 20s. And anyway the little hammer handle pike can keep you interested despite the disappointment when you see them.
So Ive been putting together a selection of little baitfish first, while I wat for bigger jig hooks to arrive. Essentially I'm copying the sizes and colours I used to like in the old, and sadly discontinued, Fox chubby shads. The other think I aim for is flies that, as far as possible, match the presentations that lure anglers use most often: neutrally buoyant bait fish to copy suspending cranks, jigs for hopping and dragging, weighted swim flies, topwaters and some magic heads for wiggle. I might even do something as heretical as add a spinner blade to some of them but I don't know yet.
I'm almost looking forward to the perch fishing more than the highland pike!