The only fly rod walleye I have ever caught were all in a midsize pond (3.5 acres or so). My big water CT walleye were all on stick baits or soft plastics before that. Until twilight last night I had yet to nail a fly rod walleye on bigger water.
I should be clear here: I use two fly rigs in my lake not because of the large perch population, rather in spite of it. I use a two nymph rig because the primary forage fish are yearling bass and bluegills, and small minnows, all of which are schooling fish. Therefore the more school-like your rig is the better the chances a predatory fish will take on of the flies. Usually I'm expecting largemouth or smallmouth bass. I know walleye sometimes eat insects. I've seen it happen. I also know they eat lots of small baitfish. That didn't stop me from being surprised when my top Hare's Ear was wonked by a big one about ten feet from my rod tip just after sunset at the boat launch! I was pretty thrilled, it has been a little while since my last walleye.