Quentin, I'm going on what stillwater trout anglers experienced in the UK when Carp were surface feeding. We would fish a floating fry pattern (about 1 inch long) during August which would be a killer on big rainbows in lakes at that time of year. The floating fry is basically a piece of white foam cut to shape like a fish which is lashed to a size 10 or 8 hook. Ocaisionally an angler would get more than he bargained for when connecting with a 20lb plus Common Carp. Never happened to me but frequently enough to be more than chance.
A bit "non-purist" but you can rig some floating carp baits on hooks and cast them with a fly rod.
Otherwise the "Dog Biscuit" pattern is right on the money